Methods for the stereoselective synthesis of substituted piperidines

ABSTRACT

One aspect of the present invention relates to methods of synthesizing substituted piperidines. A second aspect of the present invention relates to stereoselective methods of synthesizing substituted piperidines. The methods of the present invention will find use in the synthesis of compounds useful for treatment of numerous ailments, conditions and diseases that afflict mammals, including but not limited to addiction and pain. An additional aspect of the present invention relates to the synthesis of combinatorial libraries of the substituted piperidines using the methods of the present invention. An additional aspect of the present invention relates to enantiomerically substituted pyrrolidines, piperidines, and azepines.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/012,242, filed Dec. 4, 2001, now U.S. Pat. No. 6,703,508; whichclaims the benefit of priority to U.S. Provisional Patent ApplicationsSer. Nos. 60/251,209, filed Dec. 4, 2000; and 60/275,600, filed Mar. 13,2001.

BACKGROUND OF THE INVENTION

Pain is an unpleasant sensation varying in severity in a local part ofthe body or several parts of the body resulting from injury, disease, oremotional disorder. Pain can be classified according to its duration.Acute pain, which lasts less than one month, usually has a readilyidentifiable cause and signals tissue damage. In addition, acute painsyndromes can be episodic, for example recurrent discomfort fromarthritis. Chronic pain can be defined as pain that persists more thanone month beyond the usual course of an acute illness or injury, or painthat recurs at intervals over months or years, or pain that isassociated with a chronic pathologic process. In contrast to acute pain,chronic pain loses its adaptive biologic function. Depression is common,and abnormal illness behavior often compounds the patient's impairment.

Millions of people suffer from chronic or intractable pain. Persistentpain varies in etiology and presentation. In some cases, symptoms andsigns may be evident within a few weeks to a few months after theoccurrence of an injury or the onset of disease, e.g. cancer or AIDS.Like many illnesses that at one time were not well understood, pain andits many manifestations may be poorly treated and seriouslyunderestimated. Inappropriately treated pain seriously compromises thepatient's quality of life, causing emotional suffering and increasingthe risk of lost livelihood and disrupted social integration. Severechronic pain affects both the pediatric and adult population, and oftenleads to mood disorders, including depression and, in rare cases,suicide.

In the last several years, health policy-makers, health professionals,regulators, and the public have become increasingly interested in theprovision of better pain therapies. This interest is evidenced, in part,by the U.S. Department of Health and Human Services' dissemination ofClinical Practice Guidelines for the management of acute pain and cancerpain. There is currently no nationally accepted consensus for thetreatment of chronic pain not due to cancer, yet the economic and socialcosts of chronic pain are substantial, with estimates ranging in thetens of billions of dollars annually.

Three general classes of drugs are currently available for painmanagement, nonsteriodal anti-inflammatories, opioidids, and adjuvantanalgesics. The nonsteriodal anti-inflammatories class includes drugssuch as aspirin, ibuprofen, diclofenac, acetaminophen, celecoxib, androfecoxib. The opioid class includes morphine, oxycodone, fentanyl, andpentazocine. Adjuvant analgesics include various antidepressants,anticonvulsants, neuroleptics, and corticosteroids.

Opioids are the major class of analgesics used in the management ofmoderate to severe pain because of their effectiveness, ease oftitration, and favorable risk-to-benefit ratio. Opioids produceanalgesia by binding to specific receptors both within and outside theCNS. Opioid analgesics are classified as full agonists, partialagonists, or mixed agonist-antagonists, depending on the receptors towhich they bind and their intrinsic activities at each receptor.

Three subclasses of opioid receptor have been identified in humans,namely the δ-, κ-, and μ-opioid receptors. Analgesia is thought toinvolve activation of μ and/or κ receptors. Notwithstanding their lowselectivity for μ over κ receptors, it is likely that morphine andmorphine-like opioid agonists produce analgesia primarily throughinteraction with μ receptors; selective agonists of κ receptors inhumans produce analgesia, because rather than the euphoria associatedwith morphine and congeners, these compounds often produce dysphoria andpsychotomimetic effects. The consequences of activating δ receptors inhumans remain unclear.

Although opioids can be very effective in pain management, they do causeseveral side effects, such as respiratory depression, constipation,physical dependence, tolerance, and withdrawal. These unwanted effectscan severely limit their use.

Opioids are known to produce respiratory depression that is proportionalto their analgesia. This respiratory depression can be life threatening.This results in a narrow range between the effective dose and a dosethat produces respiratory depression. Because of this narrow therapeuticindex, patients receiving opioid therapy must be closely monitored forsigns of respiratory failure.

Opioids can also cause constipation in individuals receiving them. Thisside effect can be severe and may require prolonged hospitalization, oreven surgical intervention.

Commonly used full agonists include morphine, hydromorphone, meperidine,methadone, levorphanol, and fentanyl. These opioids are classified asfull agonists because there is not a ceiling to their analgesicefficacy, nor will they reverse or antagonize the effects of otheropioids within this class when given simultaneously. Side effectsinclude respiratory depression, constipation, nausea, urinary retention,confusion, and sedation. Morphine is the most commonly used opioid formoderate to severe pain because of its availability in a wide variety ofdosage forms, its well-characterized pharmacokinetics andpharmacodynamics, and its relatively low cost. Meperidine may be usefulfor brief courses (e.g., a few days) to treat acute pain and to managerigors (shivering) induced by medication, but it generally should beavoided in patients with cancer because of its short duration of action(2.5 to 3.5 hours) and its toxic metabolite, normeperidine. Thismetabolite accumulates, particularly when renal function is impaired,and causes CNS stimulation, which may lead to dysphoria, agitation, andseizures; meperidine, therefore, should not be used if continued opioiduse is anticipated.

The development of physical dependence with repeated use is acharacteristic feature of the opioid drugs, and the possibility ofdeveloping drug dependence is one of the major limitations of theirclinical use. Almost all opioid users rapidly develop drug dependencywhich can lead to apathy, weight loss, loss of sex drive, anxiety,insomnia, and drug cravings. Although physical dependence is common,addiction and abuse are not common in pain patients who are treatedappropriately with opioid drugs.

Historically, the development of analgesic tolerance was believed tolimit the ability to use opioids efficaciously on a long-term basis forpain management. Tolerance, or decreasing pain relief with the samedosage over time, has not proven to be a prevalent limitation tolong-term opioid use. Experience with treating cancer pain has shownthat what initially appears to be tolerance is usually progression ofthe disease. Furthermore, for most opioids, there does not appear to bean arbitrary upper dosage limit, as was once thought.

Cessation of opioid administration may result in a withdrawal syndrome.Symptoms of withdrawal are often the opposite of the effects achieved bythe drug; withdrawal from morphine, however, results in complex symptomsthat may seem unrelated to its effects. Misunderstanding of addictionand mislabeling of patients as addicts result in unnecessary withholdingof opioid medications. Addiction is a compulsive disorder in which anindividual becomes preoccupied with obtaining and using a substance, thecontinued use of which results in a decreased quality of life. Studiesindicate that the de novo development of addiction is low when opioidsare used for the relief of pain. Furthermore, even opioid addicts canbenefit from the carefully supervised, judicious use of opioids for thetreatment of pain due to cancer, surgery, or recurrent painful illnessessuch as sickle cell disease.

The known opioids have been very effective in pain management. However,they have restricted use because of several potentially severe sideeffects. Therefore, there is a current need for pharmaceutical agentsthat retain the analgesic properties of the known opioid, but that havereduced side effect profiles.

Additionally, dopamine, norepinephrine and serotonin are mammalianmonoamine neurotransmitters that play important roles in a wide varietyof physiological processes. Therefore, compounds that selectivelymodulate the activity of these three neurotransmitters, eitherindividually, in pairs, or as a group, promise to serve as agentseffective in the treatment of a wide range of maladies, conditions anddiseases that afflict mammals due to atypical activities of theseneurotransmitters. Interestingly, a significant portion of the knowncompounds that modulate the activity of these three neurotransmitters,either individually, in pairs, or as a group, comprise a substitutedpiperidine moiety.

Dopamine plays a major role in addiction. Many of the concepts thatapply to dopamine apply to other neurotransmitters as well. As achemical messenger, dopamine is similar to adrenaline. Dopamine affectsbrain processes that control movement, emotional response, and abilityto experience pleasure and pain. Regulation of dopamine plays a crucialrole in our mental and physical health. Neurons containing theneurotransmitter dopamine are clustered in the midbrain in an areacalled the substantia nigra. In Parkinson's disease, thedopamine-transmitting neurons in this area die. As a result, the brainsof people with Parkinson's disease contain almost no dopamine. To helprelieve their symptoms, these patients are given L-DOPA, a drug that canbe converted in the brain to dopamine.

Norepinephrine, also called noradrenaline, is a neurotransmitter thatalso acts as a hormone. As a neurotransmitter, norepinephrine helps toregulate arousal, dreaming, and moods. As a hormone, it acts to increaseblood pressure, constrict blood vessels and increase heartrate—responses that occur when we feel stress.

Serotonin (5-hydroxytryptamine, 5-HT) is widely distributed in animalsand plants, occurring in vertebrates, fruits, nuts, and venoms. A numberof congeners of serotonin are also found in nature and have been shownto possess a variety of peripheral and central nervous systemactivities. Serotonin may be obtained from a variety of dietary sources;however, endogenous 5-HT is synthesized in situ from tryptophan throughthe actions of the enzymes tryptophan hydroxylase and aromatic L-aminoacid decarboxylase. Both dietary and endogenous 5-HT are rapidlymetabolized and inactivated by monoamine oxidase and aldehydedehydrogenase to the major metabolite, 5-hydroxyindoleacetic acid(5-HIAA).

Serotonin is implicated in the etiology or treatment of variousdisorders, particularly those of the central nervous system, includinganxiety, depression, obsessive-compulsive disorder, schizophrenia,stroke, obesity, pain, hypertension, vascular disorders, migraine, andnausea. Recently, understanding of the role of 5-HT in these and otherdisorders has advanced rapidly due to increasing understanding of thephysiological role of various serotonin receptor subtypes.

Although various methods have been reported for laboratory synthesis ofpiperidines, the vast majority of these methods are not suitable for acommercial-scale process. Moreover, there are no reliablestereoselective methods for the controled asymmetric synthesis ofsubstituted piperidines. The disadvantages of the traditional syntheticmethods include modest overall yields and poor stereoselectivities.Moreover, small amounts of by-products, such as undesired stereoisomers,often accumulate during the synthetic protocol, making completepurification of the final product difficult.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to methods of synthesizingsubstituted piperidines. A second aspect of the present inventionrelates to stereoselective methods of synthesizing substitutedpiperidines. The methods of the present invention will find use in thesynthesis of compounds useful for treatment of numerous ailments,conditions and diseases that afflict mammals, including but not limitedto addiction and pain. An additional aspect of the present inventionrelates to the synthesis of combinatorial libraries of the substitutedpiperidines using the methods of the present invention. An additionalaspect of the present invention relates to enantiomerically substitutedpyrrolidines, piperidines, and azepines.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts certain structural classes of substituted piperidinesthat can be prepared according to the methods of the present invention.

FIG. 2 depicts a proposed asymmetric synthesis of a 3-substitutedpiperidine.

FIG. 3 depicts a proposed asymmetric synthesis of a 3-substitutedpiperidine.

FIG. 4 depicts a proposed asymmetric synthesis of a 3-substitutedpiperidine.

FIG. 5 depicts a proposed asymmetric synthesis of a 3-substitutedpiperidine.

FIG. 6 depicts a proposed asymmetric synthesis of a 3-substitutedpiperidine.

FIG. 7 depicts schematically synthetic routes to compounds 37 and 2.

FIG. 8 depicts schematically synthetic routes to compounds 35 and 36.

FIG. 9 depicts schematically a synthetic route to compounds 9 and 12.

FIG. 10 depicts schematically a synthetic route to compounds 17, 19, 33,and 34.

FIG. 11 depicts an HPLC chromatogram of a mixture of stereoisomers 15,16, 27, and 28.

FIG. 12 depicts the HPLC chromatogram of purified stereoisomer 15 (R,S).

FIG. 13 depicts the HPLC chromatograms of purified stereoisomer 27(S,S).

FIG. 14 depicts the HPLC chromatograms of purified stereoisomer 16(R,R).

FIG. 15 depicts the HPLC chromatogram of purified stereoisomer 28 (S,R).

FIG. 16 depicts peak retention times obtained from HPLC traces forvarious mixtures comprising a compound prepared according to the methodsof the present invention.

FIG. 17 depicts peak retention times obtained from HPLC traces forvarious mixtures comprising a compound prepared according to the methodsof the present invention.

FIG. 18 depicts peak retention times obtained from HPLC traces forvarious mixtures comprising a compound prepared according to the methodsof the present invention.

FIG. 19 depicts HPLC traces for various mixtures comprising a compoundprepared according to the methods of the present invention.

FIG. 20 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 21 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 22 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 23 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 24 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 25 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 26 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 27 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 28 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 29 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 30 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 31 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 32 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 33 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 34 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 35 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 36 depicts various asymmetric ligands that may be comprised by theasymmetric catalysts utilized in the asymmetric synthetic methods of thepresent invention.

FIG. 37 depicts various sources of nucleophilic carbon that may beutilized in the asymmetric synthetic methods of the present invention.

FIG. 38 depicts various sources of nucleophilic carbon that may beutilized in the asymmetric synthetic methods of the present invention.

FIG. 39 depicts an ORTEP drawing of the X-ray crystal structure ofcompound 2.

FIG. 40 depicts an HPLC chromatogram of a mixture of stereoisomers 1, 2,3, and 4.

FIG. 41 depicts the HPLC chromatogram of purified stereoisomer 2 (R,S).

DETAILED DESCRIPTION OF THE INVENTION

Pain is an unpleasant sensation varying in severity in a local part ofthe body or several parts of the body resulting from injury, disease, oremotional disorder. Pain can be classified according to its duration.Acute pain, which lasts less than one month, usually has a readilyidentifiable cause (e.g., hip fracture) and signals tissue damage. Theassociated effect is often anxiety, and the concomitant physiologicfindings are those of sympathetic stimulation (e.g., tachycardia,tachypnea, diaphoresis). In addition, acute pain syndromes can beepisodic, for example recurrent discomfort from arthritis.

Chronic pain can be defined as pain that persists more than one monthbeyond the usual course of an acute illness or injury, or pain thatrecurs at intervals over months or years, or pain that is associatedwith a chronic pathologic process. In contrast to acute pain, chronicpain loses its adaptive biologic function. Depression is common, andabnormal illness behavior often compounds the patient's impairment.Chronic pain can be divided broadly into that which is inferred to bepredominantly somatogenic and that which is inferred to be predominantlypsychogenic. A similar classification based on inferred pathophysiologydesignates chronic pain as nociceptive (commensurate with ongoingactivation of pain-sensitive nerve fibers), neuropathic (due to aberrantsomatosensory processing in afferent neural pathways), or psychogenic.

Nociceptive pain can be somatic or visceral. Most chronic pain in theelderly is nociceptive and somatic; arthritis, cancer pain, andmyofascial pain are most common. Relief is likely with removal of theperipheral cause (e.g., reducing periarticular inflammation), andanalgesic drugs are often effective.

A common subtype of neuropathic pain, known collectively as peripheralneuropathic pain, is presumably sustained by mechanisms that involvedisturbances in the peripheral nerve or nerve root; neuroma formationafter axonal injury and nerve compression are the two major processes.Another subtype of neuropathic pain is related to the reorganization ofnociceptive information processing by the CNS; it persists withoutongoing activation of pain-sensitive fibers. This type of pain, knowncollectively as the deafferentation syndromes, includes postherpeticneuralgia, central pain (which can result from a lesion at any level ofthe CNS), phantom limb pain, and others. A third subtype of neuropathicpain, often called sympathetically maintained pain, can be amelioratedby interruption of sympathetic nerves to the painful area; theprototypic disorder is reflex sympathetic dystrophy. The precisemechanisms involved in these disorders are conjectural, but all canproduce an unfamiliar pain, often described as burning and stabbing.Currently, this type of pain responds poorly to analgesics.

Some patients have persistent pain without either nociceptive foci orevidence of a neuropathic mechanism for the pain. Many others havenociceptive lesions that do not sufficiently explain the degree of painand disability. Psychopathologic processes account for these complaintsin some patients. If no evidence for a psychological cause is found, thepain is referred to as idiopathic. Many patients have an idiopathic painsyndrome that is best described by the generic diagnosis chronicnonmalignant pain syndrome, a term denoting pain and disabilitydisproportionate to an identifiable somatic cause and usually related toa more pervasive set of abnormal illness behaviors. Some of thesepatients may be labeled by the more formal psychiatric diagnosis ofsomatoform pain disorder. Others have complaints that constitute aspecific pain diagnosis, most commonly the failed low back syndrome oratypical facial pain. Still others have significant organic lesions(e.g., lumbar arachnoiditis) but also have a clear psychologicalcontribution associated with excessive disability. Diagnosis may bedifficult, but the relative contributions of both organic andpsychological components of the pain can be defined.

Another clinically useful classification of chronic pain is broadlysyndromic. For example, chronic pain may be part of a medical illness(e.g., cancer or arthritis). A mixture of pathophysiologic mechanismsmay be involved; e.g., tumor invasion of nerve and bone may causeneuropathic and somatic nociceptive pains, respectively, andpsychological factors may be prominent.

Three general classes of drugs are currently available for painmanagement, nonsteriodal anti-inflammatories, opioids, and adjuvantanalgesics. The nonsteriodal anti-inflammatories class includes drugssuch as aspirin, ibuprofen, diclofenac, acetaminophen, and rofecoxib.The opioid class includes morphine, oxycodone, fentanyl, andpentazocine. Adjuvant analgesics include various antidepressants,anticonvulsants, neuroleptics, and corticosteroids.

Of the three classes of pharmaceutical agents used for pain management,opioid are usually most efficacious for treating moderate to severepain. Although opioids can be very effective in pain management, they docause several side effects, such as respiratory depression,constipation, physical dependence, tolerance, withdraw. These unwantedeffects can severely limit their use. Therefore, there is a current needfor pharmaceutical agents that retain the analgesic properties of theknown opioid, but have reduced side effect profiles for the treatment ofpain.

Opioids, specifically ligands for the μ-opioid receptor, are the majorclass of analgesics used in the management of moderate to severe painbecause of their effectiveness, ease of titration, and favorablerisk-to-benefit ratio. Unfortunately, the opioids currently availablehave several unwanted side-effects, such as respiratory depression andconstipation. In addition, these agents may lead to tolerance anddependence. Research into the development of new, selective ligands foropioid receptors holds the promise of yielding potent analgesics thatlack the side effects of morphine and its congeners. Applicants hereindisclose novel analgesics, including selective ligands for opioidreceptors. Individual compounds described herein promise to haveagonistic, antagonistic, and hybrid effects on opioid and other cellularreceptors. Additionally, new compounds reported herein may possessanalgesic properties free from respiratory depression and the potentialfor physical dependence associated with μ-opioid receptor ligands, suchas morphine and fentanyl. Moreover, new compounds reported herein maypossess properties for the treatment of physical or psychologicaladditions, psychiatric disorders, and neurological pathologies, such astinnitus.

The μ-opioid receptor is a member of a family of cell surface proteinsthat permit intracellular transduction of extracellular signals. Cellsurface proteins provide eukaryotic and prokaryotic cells a means todetect extracellular signals and transduce such signals intracellularlyin a manner that ultimately results in a cellular response or aconcerted tissue or organ response. Cell surface proteins, byintracellularly transmitting information regarding the extracellularenvironment via specific intracellular pathways induce an appropriateresponse to a particular stimulus. The response may be immediate andtransient, slow and sustained, or some mixture thereof. By virtue of anarray of varied membrane surface proteins, eukaryotic cells areexquisitely sensitive to their environment.

Definitions

For convenience, certain terms employed in the specification, examples,and appended claims are collected here.

The term “heteroatom” as used herein means an atom of any element otherthan carbon or hydrogen. Preferred heteroatoms are boron, nitrogen,oxygen, phosphorus, sulfur and selenium.

The term “electron-withdrawing group” is recognized in the art, anddenotes the tendency of a substituent to attract valence electrons fromneighboring atoms, i.e., the substituent is electronegative with respectto neighboring atoms. A quantification of the level ofelectron-withdrawing capability is given by the Hammett sigma (σ)constant. This well known constant is described in many references, forinstance, J. March, Advanced Organic Chemistry, McGraw Hill BookCompany, New York, (1977 edition) pp. 251–259. The Hammett constantvalues are generally negative for electron donating groups (σ[P]=−0.66for NH₂) and positive for electron withdrawing groups (σ[P]=0.78 for anitro group), σ[P] indicating para substitution. Exemplaryelectron-withdrawing groups include nitro, acyl, formyl, sulfonyl,trifluoromethyl, cyano, chloride, and the like. Exemplaryelectron-donating groups include amino, methoxy, and the like.

The term “alkyl” refers to the radical of saturated aliphatic groups,including straight-chain alkyl groups, branched-chain alkyl groups,cycloalkyl (alicyclic) groups, alkyl substituted cycloalkyl groups, andcycloalkyl substituted alkyl groups. In preferred embodiments, astraight chain or branched chain alkyl has 30 or fewer carbon atoms inits backbone (e.g., C₁–C₃₀ for straight chain, C₃–C–₃₀ for branchedchain), and more preferably 20 or fewer. Likewise, preferred cycloalkylshave from 3–10 carbon atoms in their ring structure, and more preferablyhave 5, 6 or 7 carbons in the ring structure.

Unless the number of carbons is otherwise specified, “lower alkyl” asused herein means an alkyl group, as defined above, but having from oneto ten carbons, more preferably from one to six carbon atoms in itsbackbone structure. Likewise, “lower alkenyl” and “lower alkynyl” havesimilar chain lengths. Preferred alkyl groups are lower alkyls. Inpreferred embodiments, a substituent designated herein as alkyl is alower alkyl.

The term “aralkyl”, as used herein, refers to an alkyl group substitutedwith an aryl group (e.g., an aromatic or heteroaromatic group).

The terms “alkenyl” and “alkynyl” refer to unsaturated aliphatic groupsanalogous in length and possible substitution to the alkyls describedabove, but that contain at least one double or triple bond respectively.

The term “aryl” as used herein includes 5-, 6- and 7-memberedsingle-ring aromatic groups that may include from zero to fourheteroatoms, for example, benzene, pyrrole, furan, thiophene, imidazole,oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazineand pyrimidine, and the like. Those aryl groups having heteroatoms inthe ring structure may also be referred to as “aryl heterocycles” or“heteroaromatics.” The aromatic ring can be substituted at one or morering positions with such substituents as described above, for example,halogen, azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl,alkoxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate,phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl,sulfonamido, ketone, aldehyde, ester, heterocyclyl, aromatic orheteroaromatic moieties, —CF₃, —CN, or the like. The term “aryl” alsoincludes polycyclic ring systems having two or more cyclic rings inwhich two or more carbons are common to two adjoining rings (the ringsare “fused rings”) wherein at least one of the rings is aromatic, e.g.,the other cyclic rings can be cycloalkyls, cycloalkenyls, cycloalkynyls,aryls and/or heterocyclyls.

The terms ortho, meta and para apply to 1,2-, 1,3- and 1,4-disubstitutedbenzenes, respectively. For example, the names 1,2-dimethylbenzene andortho-dimethylbenzene are synonymous.

The terms “heterocyclyl” or “heterocyclic group” refer to 3- to10-membered ring structures, more preferably 3- to 7-membered rings,whose ring structures include one to four heteroatoms. Heterocycles canalso be polycycles. Heterocyclyl groups include, for example, thiophene,thianthrene, furan, pyran, isobenzofuran, chromene, xanthene,phenoxathiin, pyrrole, imidazole, pyrazole, isothiazole, isoxazole,pyridine, pyrazine, pyrimidine, pyridazine, indolizine, isoindole,indole, indazole, purine, quinolizine, isoquinoline, quinoline,phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline,pteridine, carbazole, carboline, phenanthridine, acridine, pyrimidine,phenanthroline, phenazine, phenarsazine, phenothiazine, furazan,phenoxazine, pyrrolidine, oxolane, thiolane, oxazole, piperidine,piperazine, morpholine, lactones, lactams such as azetidinones andpyrrolidinones, sultams, sultones, and the like. The heterocyclic ringcan be substituted at one or more positions with such substituents asdescribed above, as for example, halogen, alkyl, aralkyl, alkenyl,alkynyl, cycloalkyl, hydroxyl, amino, nitro, sulfhydryl, imino, amido,phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio,sulfonyl, ketone, aldehyde, ester, a heterocyclyl, an aromatic orheteroaromatic moiety, —CF₃, —CN, or the like.

The terms “polycyclyl” or “polycyclic group” refer to two or more rings(e.g., cycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/orheterocyclyls) in which two or more carbons are common to two adjoiningrings, e.g., the rings are “fused-rings”. Rings that are joined throughnon-adjacent atoms are termed “bridged” rings. Each of the rings of thepolycycle can be substituted with such substituents as described above,as for example, halogen, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl,hydroxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate,phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl,ketone, aldehyde, ester, a heterocyclyl, an aromatic or heteroaromaticmoiety, —CF₃, —CN, or the like.

The term “(R)-2-Methyl-CBS-oxazaborolidine” and its systematic name“(R)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole”refer to the following reagent:

The term “(S)-2-Methyl-CBS-oxazaborolidine” and its systematic name“(S)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole”refer to the following reagent:

As used herein, the term “nitro” means —NO₂; the term “halogen”designates —F, —Cl, —Br or —I; the term “sulfhydryl” means —SH; the term“hydroxyl” means —OH; and the term “sulfonyl” means —SO₂—.

The terms “amine” and “amino” are art-recognized and refer to bothunsubstituted and substituted amines, e.g., a moiety that can berepresented by the general formula:

wherein R₉, R₁₀ and R′₁₀ each independently represent a group permittedby the rules of valence.

The term “acylamino” is art-recognized and refers to a moiety that canbe represented by the general formula:

wherein R₉ represents a group permitted by the rules of valence, andR′₁₁ represents hydrogen, alkyl, cycloalkyl, alkenyl, aryl, heteroaryl,aralkyl, or heteroaralkyl.

The term “amido” is art recognized as an amino-substituted carbonyl andincludes a moiety that can be represented by the general formula:

wherein R₉, R₁₀ are as defined above. Preferred embodiments of the amidewill not include imides which may be unstable.

The term “alkylthio” refers to an alkyl group, as defined above, havinga sulfur radical attached thereto. In preferred embodiments, the“alkylthio” moiety is represented by one of —S-alkyl, —S-alkenyl, and—S-alkynyl. Representative alkylthio groups include methylthio, ethylthio, and the like.

The term “carbonyl” is art recognized and includes such moieties as canbe represented by the general formula:

wherein X is a bond or represents an oxygen or a sulfur, and R₁₁represents a hydrogen, an alkyl, an alkenyl, —(CH₂)_(m)—R₈ or apharmaceutically acceptable salt, R′₁₁ represents a hydrogen, an alkyl,an alkenyl or —(CH₂)_(m)—R₈, where m and R₈ are as defined above. WhereX is an oxygen and R₁₁ or R′₁₁ is not hydrogen, the formula representsan “ester”. Where X is an oxygen, and R₁₁ is as defined above, themoiety is referred to herein as a carboxyl group, and particularly whenR₁₁ is a hydrogen, the formula represents a “carboxylic acid”. Where Xis an oxygen, and R′₁₁ is hydrogen, the formula represents a “formate”.In general, where the oxygen atom of the above formula is replaced bysulfur, the formula represents a “thiolcarbonyl” group. Where X is asulfur and R₁₁ or R′₁₁ is not hydrogen, the formula represents a“thiolester.” Where X is a sulfur and R₁₁ is hydrogen, the formularepresents a “thiolcarboxylic acid.” Where X is a sulfur and R₁₁′ ishydrogen, the formula represents a “thiolformate.” On the other hand,where X is a bond, and R₁₁ is not hydrogen, the above formula representsa “ketone” group. Where X is a bond, and R₁₁ is hydrogen, the aboveformula represents an “aldehyde” group.

The terms “alkoxyl” or “alkoxy” as used herein refers to an alkyl group,as defined above, having an oxygen radical attached thereto.Representative alkoxyl groups include methoxy, ethoxy, propyloxy,tert-butoxy and the like. An “ether” is two hydrocarbons covalentlylinked by an oxygen. Accordingly, the substituent of an alkyl thatrenders that alkyl an ether is or resembles an alkoxyl, such as can berepresented by one of —O-alkyl, —O-alkenyl, —O-alkynyl, —O—(CH₂)_(m)—R₈,where m and R₈ are described above.

The term “sulfonate” is art recognized and includes a moiety that can berepresented by the general formula:

in which R₄₁ is an electron pair, hydrogen, alkyl, cycloalkyl, or aryl.

The terms triflyl, tosyl, mesyl, and nonaflyl are art-recognized andrefer to trifluoromethanesulfonyl, p-toluenesulfonyl, methanesulfonyl,and nonafluorobutanesulfonyl groups, respectively. The terms triflate,tosylate, mesylate, and nonaflate are art-recognized and refer totrifluoromethanesulfonate ester, p-toluenesulfonate ester,methanesulfonate ester, and nonafluorobutanesulfonate ester functionalgroups and molecules that contain said groups, respectively.

The abbreviations Me, Et, Ph, Tf, Nf, Ts, Ms, Cbz, and Boc representmethyl, ethyl, phenyl, trifluoromethanesulfonyl,nonafluorobutanesulfonyl, p-toluenesulfonyl, methanesulfonyl,benzyloxycarbonyl, and t-butyloxycarbonyl, respectively. A morecomprehensive list of the abbreviations utilized by organic chemists ofordinary skill in the art appears in the first issue of each volume ofthe Journal of Organic Chemistry; this list is typically presented in atable entitled Standard List of Abbreviations. The abbreviationscontained in said list, and all abbreviations utilized by organicchemists of ordinary skill in the art are hereby incorporated byreference.

The term “sulfate” is art recognized and includes a moiety that can berepresented by the general formula:

in which R₄₁ is as defined above.

The term “sulfonylamino” is art recognized and includes a moiety thatcan be represented by the general formula:

The term “sulfamoyl” is art-recognized and includes a moiety that can berepresented by the general formula:

The term “sulfonyl”, as used herein, refers to a moiety that can berepresented by the general formula:

in which R₄₄ is selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl.

The term “sulfoxido” as used herein, refers to a moiety that can berepresented by the general formula:

in which R₄₄ is selected from the group consisting of hydrogen, alkyl,alkenyl, alkynyl, cycloalkyl, heterocyclyl, aralkyl, or aryl.

A “selenoalkyl” refers to an alkyl group having a substituted selenogroup attached thereto. Exemplary “selenoethers” which may besubstituted on the alkyl are selected from one of —Se-alkyl,—Se-alkenyl, and —Se-alkynyl.

Analogous substitutions can be made to alkenyl and alkynyl groups toproduce, for example, aminoalkenyls, aminoalkynyls, amidoalkenyls,amidoalkynyls, iminoalkenyls, iminoalkynyls, thioalkenyls, thioalkynyls,carbonyl-substituted alkenyls or alkynyls.

As used herein, the definition of each expression, e.g. alkyl, m, n,etc., when it occurs more than once in any structure, is intended to beindependent of its definition elsewhere in the same structure.

It will be understood that “substitution” or “substituted with” includesthe implicit proviso that such substitution is in accordance withpermitted valence of the substituted atom and the substituent, and thatthe substitution results in a stable compound, e.g., which does notspontaneously undergo transformation such as by rearrangement,cyclization, elimination, etc.

As used herein, the term “substituted” is contemplated to include allpermissible substituents of organic compounds. In a broad aspect, thepermissible substituents include acyclic and cyclic, branched andunbranched, carbocyclic and heterocyclic, aromatic and nonaromaticsubstituents of organic compounds. Illustrative substituents include,for example, those described herein above. The permissible substituentscan be one or more and the same or different for appropriate organiccompounds. For purposes of this invention, the heteroatoms such asnitrogen may have hydrogen substituents and/or any permissiblesubstituents of organic compounds described herein which satisfy thevalences of the heteroatoms. This invention is not intended to belimited in any manner by the permissible substituents of organiccompounds.

The phrase “protecting group” as used herein means temporarysubstituents which protect a potentially reactive functional group fromundesired chemical transformations. Examples of such protecting groupsinclude esters of carboxylic acids, silyl ethers of alcohols, carbamatesof amines, ureas of amines, and acetals and ketals of aldehydes andketones, respectively. The field of protecting group chemistry has beenreviewed (Greene, T. W. Wuts, P. G. M. Protective Groups in OrganicSynthesis, 2^(nd) ed.; Wiley: New York, 1991).

Certain compounds of the present invention may exist in particulargeometric or stereoisomeric forms. The present invention contemplatesall such compounds, including cis- and trans-isomers, R- andS-enantiomers, diastereomers, (D)-isomers, (L)-isomers, the racemicmixtures thereof, and other mixtures thereof, as falling within thescope of the invention. Additional asymmetric carbon atoms may bepresent in a substituent such as an alkyl group. All such isomers, aswell as mixtures thereof, are intended to be included in this invention.

If, for instance, a particular enantiomer of a compound of the presentinvention is desired, it may be prepared by asymmetric synthesis, or byderivation with a chiral auxiliary, where the resulting diastereomericmixture is separated and the auxiliary group cleaved to provide the puredesired enantiomers. Alternatively, where the molecule contains a basicfunctional group, such as amino, or an acidic functional group, such ascarboxyl, diastereomeric salts are formed with an appropriateoptically-active acid or base, followed by resolution of thediastereomers thus formed by fractional crystallization orchromatographic means well known in the art, and subsequent recovery ofthe pure enantiomers.

Contemplated equivalents of the compounds described above includecompounds which otherwise correspond thereto, and which have the samegeneral properties thereof (e.g., functioning as analgesics), whereinone or more simple variations of substituents are made which do notadversely affect the efficacy of the compound in binding to opioidreceptors. In general, the compounds of the present invention may beprepared by the methods illustrated in the general reaction schemes as,for example, described below, or by modifications thereof, using readilyavailable starting materials, reagents and conventional synthesisprocedures. In these reactions, it is also possible to make use ofvariants which are in themselves known, but are not mentioned here.

For purposes of this invention, the chemical elements are identified inaccordance with the Periodic Table of the Elements, CAS version,Handbook of Chemistry and Physics, 67th Ed., 1986–87, inside cover.

Compounds of the Invention

The compounds of the present invention are enantiomerically-enrichedsubstituted pyrrolidines, piperidines, and azepines useful for treatmentof numerous ailments, conditions and diseases that afflict mammals,including but not limited to addiction and pain (see FIG. 1).

In certain embodiments, a compound of the present invention isrepresented by formula I:

wherein

n is 0, 1, or 2;

R is H, aralkyl, or —CO₂R′;

R′ is alkyl, aryl, or aralkyl;

Z is NHR″ or OH; and

R″ is H, alkyl, aryl, or aralkyl.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein R isCbz.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein R is—CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein R is H.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein R′ ismethyl.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein Z isNHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;and R′ is Me.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R′ is Me; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R′ is Me; Z is OH; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R′ is Me; Z is NHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R′ is Me; Z is NHR″; R″ is phenyl; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R is Cbz; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;and R is —CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; R′ is methyl; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula I and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; R′ is methyl; Z is NHR″; and R″ is phenyl.

In certain embodiments, a compound of the present invention isrepresented by formula II:

wherein

n is 0, 1, or 2;

R is H, aralkyl, or —CO₂R′;

R′ is alkyl, aryl, or aralkyl;

Z is NHR″ or OH; and

R″ is H, alkyl, aryl, or aralkyl.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein R isCbz.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein R is—CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein R is H.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein R′ ismethyl.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein Z isOH.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein Z isNHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;and R′ is Me.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R′ is Me; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R′ is Me; Z is OH; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R′ is Me; Z is NHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R′ is Me; Z is NHR″; R″ is phenyl; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R is Cbz; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;and R is —CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; R′ is methyl; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula II and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; R′ is methyl; Z is NHR″; and R″ is phenyl.

In certain embodiments, a compound of the present invention isrepresented by formula III:

wherein

n is 0, 1, or 2;

R is H, aralkyl, or —CO₂R′;

R′ is alkyl, aryl, or aralkyl;

Z is NHR″ or OH; and

R″ is H, alkyl, aryl, or aralkyl.

R″ is H, alkyl, aryl, or aralkyl.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein R isCbz.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein R is—CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein R isH.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein R′ ismethyl.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein Z isOH.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein Z isNHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; and R′ is Me.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R′ is Me; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R′ is Me; Z is OH; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R′ is Me; Z is NHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R′ is Me; Z is NHR″; R″ is phenyl; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R is Cbz; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; and R is —CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R is —CH₂CH₂Ph; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R is —CH₂CH₂Ph; R′ is methyl; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula III and the attendant definitions, wherein n is1; R is —CH₂CH₂Ph; R′ is methyl; Z is NHR″; and R″ is phenyl.

In certain embodiments, a compound of the present invention isrepresented by formula IV:

wherein

n is 0, 1, or 2;

R is H, aralkyl, or —CO₂R′;

R′ is alkyl, aryl, or aralkyl;

Z is NHR″ or OH; and

R″ is H, alkyl, aryl, or aralkyl.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein R isCbz.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein R is—CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein R is H.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein R′ ismethyl.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein Z isOH.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein Z isNHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;and R′ is Me.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R′ is Me; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R′ is Me; Z is OH; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R′ is Me; Z is NHR″; and R″ is phenyl.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R′ is Me; Z is NHR″; R″ is phenyl; and R is Cbz.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R is Cbz; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;and R is —CH₂CH₂Ph.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; and R′ is methyl.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; R′ is methyl; and Z is OH.

In certain embodiments, the compounds of the present invention arerepresented by formula IV and the attendant definitions, wherein n is 1;R is —CH₂CH₂Ph; R′ is methyl; Z is NHR″; and R″ is phenyl.

Methods of the Invention

One aspect of the present invention relates to synthetic procedures forthe enantio- and diastereo-selective syntheses of each of the fourstereoisomeric compounds 1, 2, 3 and 4, which procedures are describedherein.

Several synthetic routes have been envisioned by the inventors,including several that start from 3-acylpyridine and include astereoselective reduction of the acyl carbonyl to substantially oneenantiomer of an alcohol (see FIGS. 2–4). One synthetic route inparticular is described in greater detail below and starts fromsubstantially one enantiomer of a 3-ester substituted cyclic amine. Thesynthetic route converts the ester to an aldehyde followed by astereoselective nucleophilic addition to the aldehyde to producesubstantially one enantiomer of an alcohol (see FIGS. 5 and 6).

In general, the first stereocenter (“A”) may be obtained enantiopure inthe form of a commercially available tartrate salt of ethyl nipecotate.For example, commercially available (R)-ethyl nipecotate is typically an(l)-tartaric acid (5); whereas, commercially available (S)-ethylnipecotate is typically a (d)-tartaric acid salt (6).

Enantiopure esters 5 and 6 were taken forward to aldehydes 9 and 12following the reaction scheme outlined below. Amines 5 and 6 wereprotected as carbamates 7 and 10, respectively. Other protecting groupsthat render the amine non-basic are anticipated to be acceptable.

Reduction of the ester by either a one-step or two-step protocolprovided alcohols 8 and 11. For the one step procedure, treatment ofesters 7 and 10 with lithium aluminum hydride provided the desiredalcohols 8 and 11, respectively.

For the two-step procedure, ester hydrolysis to the acid followed byborane-dimethyl sulfide reduction provided alcohols 8 and 11. Othercommonly employed reagents for the conversion of these intermediates tothe alcohol are anticipated to be acceptable.

Aldehydes 9 and 12 can be obtained using a variety of reactionconditions commonly used for such transformations. For example, it isanticipated that the esters (7 and 10), acids (25 and 26) orcorresponding acid halides could be converted directly to aldehydes 9and 12.

Aldehydes 9 and 12 were synthesized from alcohols 8 and 11 by Swernoxidation. Aldehyde 9 was also obtained by Dess-Martin oxidation. It isanticipated that Dess-Martin oxidation could be used to convert alcohol11 to aldehyde 12 equally well. Other commonly used oxidants such assuch as pyridinium chlorochromate are also anticipated to work for thistransformation.

The second stereocenter of the piperidines (“B”) was selectivelyinstalled utilizing a diastereoselective addition of dimethylzinccatalyzed by the TADDOL catalyst, developed by D. Seebach (J. L. von demBussche-Hunnefeld and D. Seebach, Tetrahedron, 1992, 48(27), 5719), toaldehydes 9 and 12. Among other catalysts, the TADDOL catalyst withAr=Phenyl and 1-naphthyl was effective; however, even better resultswere achieved with the TADDOL catalyst wherein Ar=2-naphthyl. Bychoosing the correct TADDOL catalyst enantiomer (13 or 14), product witheither the (S)-(15) or (R)-(16) configuration for stereocenter “B” wasachieved. Assignment of stereochemistry was made based on literatureprecedents. Catalyst 13 promotes addition to the si face to form 15 (RS)and 27 (SS) from aldehydes 9 and 12, respectively; whereas, catalyst 14promotes addition to the re face to form alcohol 16 (RR) and 28 (SR)from aldehydes 9 and 12, respectively.

In certain embodiments, the use of about 5 mol % to about 20 mol %TADDOL is preferred. In certain embodiments, the use of about 15 mol %TADDOL is preferred. In certain embodiments, the use of about 10 mol %TADDOL is preferred. In certain embodiments, the use of freshlydistilled titanium tetraisopropoxide and dimethyl zinc is preferred.Furthermore, catalyst derived from recovered TADDOL ligand may be usedwith no loss in yields and selectivities.

It is anticipated that other chiral catalysts and reagents designed tostereoselectively add alkyl groups, such as methyl, to aldehydes willwork in the methods of the present invention. For a recent review, whichis hereby expressly incorporated by reference, see: Pu, L, Yu, H.-B.“Catalytic Asymmetric Organozinc Additions to Carbonyl Compounds” Chem.Rev. 2001, 101, 757–824. In other words, many different chiral ligandsmay be used in conjunction with a transition metal to catalyze thistransformation. Examples of such catalysts and/or ligands include chiralamino alcohols, chiral iminyl alcohols, chiral amino thiols, chiraldisulfides, chiral diselenides, chiral amines, chiral diols, chiralsulfonamides, chiral phosphoramides, chiral ligands attached to solidsupports, chiral dendrites, and chiral polymers. Various examples ofeach type of ligand are depicted in FIGS. 20–36. The catalysts for thistransformation may be isolated or generated in situ by a complex of anyof the above ligands with titanium, zinc, iron, ruthenium, chromium,zirconium, nobium, manganese, lead, calcium, boron, lithium, cadmium,aluminum, tin, or copper. There are many sources of nucleophilic carbonfor this transformation, e.g., dimethyl zinc; various examples ofnucleophilic carbon sources are depicted in FIGS. 37 and 38.

Once both stereocenters are established, completion of the synthesis toselectively form 1, 2, 3 and 4 is straightforward (see FIGS. 7–10).Alcohols 15, 16, 27 and 28 were converted to the corresponding mesylateswith mesyl chloride. S_(N)2 displacement with aniline provided amines17, 19, 33 and 34, respectively. No loss of enantiopurity was observedfor the aniline displacement reaction.

The conversion of the alcohols to the corresponding amines can also beaccomplished by conversion of the alcohol to a triflate, with subsequentS_(N)2 displacement by aniline. This alternative protocol wasdemonstrated by the conversion of alcohol 15 to amine 17. Thistransformation has been run in one pot without isolation or purificationof the triflate intermediate. Furthermore, the amine product was easilyobtained with high levels of purity, allowing for higher yields in thesubsequent acylation step described below.

Acylation of amines 17, 19, 33, and 34 with propionyl chloride providedamides 18, 20, 35 and 36. Acylation with other reagents such aspropionic anhydride or propionic acids activated with a reagent such asPyBOP are also anticipated to work for this transformation.

Cbz deprotection was straightforward, as was represented by theconversions of 18 and 20 to secondary amines 37 and 38.

These secondary amines may be converted to a variety of products, suchas amides, sulfonamides, ureas, and carbamates. In certain preferredembodiments, the secondary amines are converted to tertiary amineproducts, such as compounds 1, 2, 3 and 4. In the case of 1–4, treatmentwith a phenethylhalide and a base such as K₂CO₃ may be used. This wasdemonstrated by the chemistry described below for the synthesis of amixture of 1–4. Of course, one of ordinary skill in the art of organicchemistry will recognize that other methods, e.g., reductive amination,may be used to achieve these alkylations.

As was noted above, it is anticipated that the chemistries describedabove should work well with BOC protected amine compounds. This wasdemonstrated in the non-selective synthesis of 24, a mixture of isomers1–4. 24 was synthesized from alcohol 21, which differs from 15 and 16only in its carbamate protecting group (BOC instead of Cbz), and itslack of enantio- and diastereo-purity. Compound 21 was obtained byGrignard addition to the corresponding aldehyde. For the stereoselectivechemistry described above, N-Cbz protection was chosen over N-BOCprotection based only on the fact that the Cbz-compounds have a betterchromophore (compared to BOC protected compounds) for analytical HPLC eeand de determinations of intermediates on the route to compounds 1 to 4.

Compound 24 was separated into the four individual isomers, 1–4, byachiral and chiral chromatographic methods. Furthermore, all fourisomers (1–4) were separated by analytical chiral HPLC methods. Theabsolute stereochemistry of all four isomers (obtained by separation of24) was determined using x-ray crystallographic and other analyticalmethods. The absolute stereochemistry of 2 was determined by x-raycrystallography. FIG. 39. This information was then combined with otheranalytical methods to determine the absolute stereochemistry of all fourisomers (1 to 4). Using these authentic samples, the stereochemistryassigned for the products 15, 16, 27 and 28 were confirmed. AnalyticalHPLC comparison of 2, synthesized stereoselectively by the methodsdescribed herein, matched the known sample of 2, synthesized byseparation of 24.

Combinatorial Libraries

The subject methods may be practiced in a combinatorial sense to preparecombinatorial libraries of substituted piperidines for the screening ofpharmaceutical, agrochemical or other biological or medically-relatedactivity or material-related qualities. A combinatorial library for thepurposes of the present invention is a mixture of chemically relatedcompounds which may be screened together for a desired property; saidlibraries may be in solution or covalently linked to a solid support.The preparation of many related compounds in a single reaction greatlyreduces and simplifies the number of screening processes which need tobe carried out. Screening for the appropriate biological,pharmaceutical, agrochemical or physical property may be done byconventional methods.

Diversity in a library can be created at a variety of different levels.For instance, the substrate aryl groups used in a combinatorial approachcan be diverse in terms of the core aryl moiety, e.g., a variegation interms of the ring structure, and/or can be varied with respect to theother substituents.

A variety of techniques are available in the art for generatingcombinatorial libraries of small organic molecules. See, for example,Blondelle et al. (1995) Trends Anal. Chem. 14:83; the Affymax U.S. Pat.Nos. 5,359,115 and 5,362,899: the Ellman U.S. Pat. No. 5,288,514: theStill et al. PCT publication WO 94/08051; Chen et al. (1994) JACS116:2661: Kerr et al. (1993) JACS 115:252; PCT publications WO92/10092,WO93/09668 and WO91/07087; and the Lerner et al. PCT publicationWO93/20242). Accordingly, a variety of libraries on the order of about16 to 1,000,000 or more diversomers can be synthesized and screened fora particular activity or property.

In an exemplary embodiment, a library of substituted diversomers can besynthesized using the subject reactions adapted to the techniquesdescribed in the Still et al. PCT publication WO 94/08051, e.g., beinglinked to a polymer bead by a hydrolyzable or photolyzable group, e.g.,located at one of the positions of substrate. According to the Still etal. technique, the library is synthesized on a set of beads, each beadincluding a set of tags identifying the particular diversomer on thatbead. In one embodiment, which is particularly suitable for discoveringenzyme inhibitors, the beads can be dispersed on the surface of apermeable membrane, and the diversomers released from the beads by lysisof the bead linker. The diversomer from each bead will diffuse acrossthe membrane to an assay zone, where it will interact with an enzymeassay. Detailed descriptions of a number of combinatorial methodologiesare provided below.

A. Direct Characterization

A growing trend in the field of combinatorial chemistry is to exploitthe sensitivity of techniques such as mass spectrometry (MS), e.g.,which can be used to characterize sub-femtomolar amounts of a compound,and to directly determine the chemical constitution of a compoundselected from a combinatorial library. For instance, where the libraryis provided on an insoluble support matrix, discrete populations ofcompounds can be first released from the support and characterized byMS. In other embodiments, as part of the MS sample preparationtechnique, such MS techniques as MALDI can be used to release a compoundfrom the matrix, particularly where a labile bond is used originally totether the compound to the matrix. For instance, a bead selected from alibrary can be irradiated in a MALDI step in order to release thediversomer from the matrix, and ionize the diversomer for MS analysis.

B) Multipin Synthesis

The libraries of the subject method can take the multipin libraryformat. Briefly, Geysen and co-workers (Geysen et al. (1984) PNAS81:3998–4002) introduced a method for generating compound libraries by aparallel synthesis on polyacrylic acid-grated polyethylene pins arrayedin the microtitre plate format. The Geysen technique can be used tosynthesize and screen thousands of compounds per week using the multipinmethod, and the tethered compounds may be reused in many assays.Appropriate linker moieties can also been appended to the pins so thatthe compounds may be cleaved from the supports after synthesis forassessment of purity and further evaluation (c.f., Bray et al. (1990)Tetrahedron Lett 31:5811–5814; Valerio et al. (1991) Anal Biochem197:168–177; Bray et al. (1991) Tetrahedron Lett 32:6163–6166).

C) Divide-Couple-Recombine

In yet another embodiment, a variegated library of compounds can beprovided on a set of beads utilizing the strategy ofdivide-couple-recombine (see, e.g., Houghten (1985) PNAS 82:5131–5135;and U.S. Pat. Nos. 4,631,211; 5,440,016; 5,480,971). Briefly, as thename implies, at each synthesis step where degeneracy is introduced intothe library, the beads are divided into separate groups equal to thenumber of different substituents to be added at a particular position inthe library, the different substituents coupled in separate reactions,and the beads recombined into one pool for the next iteration.

In one embodiment, the divide-couple-recombine strategy can be carriedout using an analogous approach to the so-called “tea bag” method firstdeveloped by Houghten, where compound synthesis occurs on resin sealedinside porous polypropylene bags (Houghten et al. (1986) PNAS82:5131–5135). Substituents are coupled to the compound-bearing resinsby placing the bags in appropriate reaction solutions, while all commonsteps such as resin washing and deprotection are performedsimultaneously in one reaction vessel. At the end of the synthesis, eachbag contains a single compound.

D) Combinatorial Libraries by Light-Directed, Spatially AddressableParallel Chemical Synthesis

A scheme of combinatorial synthesis in which the identity of a compoundis given by its locations on a synthesis substrate is termed aspatially-addressable synthesis. In one embodiment, the combinatorialprocess is carried out by controlling the addition of a chemical reagentto specific locations on a solid support (Dower et al. (1991) Annu RepMed Chem 26:271–280; Fodor, S. P. A. (1991) Science 251:767; Pirrung etal. (1992) U.S. Pat. No. 5,143,854; Jacobs et al. (1994) TrendsBiotechnol 12:19–26). The spatial resolution of photolithography affordsminiaturization. This technique can be carried out through the useprotection/deprotection reactions with photolabile protecting groups.

The key points of this technology are illustrated in Gallop et al.(1994) J Med Chem 37:1233–1251. A synthesis substrate is prepared forcoupling through the covalent attachment of photolabilenitroveratryloxycarbonyl (NVOC) protected amino linkers or otherphotolabile linkers. Light is used to selectively activate a specifiedregion of the synthesis support for coupling. Removal of the photolabileprotecting groups by light (deprotection) results in activation ofselected areas. After activation, the first of a set of amino acidanalogs, each bearing a photolabile protecting group on the aminoterminus, is exposed to the entire surface. Coupling only occurs inregions that were addressed by light in the preceding step. The reactionis stopped, the plates washed, and the substrate is again illuminatedthrough a second mask, activating a different region for reaction with asecond protected building block. The pattern of masks and the sequenceof reactants define the products and their locations. Since this processutilizes photolithography techniques, the number of compounds that canbe synthesized is limited only by the number of synthesis sites that canbe addressed with appropriate resolution. The position of each compoundis precisely known; hence, its interactions with other molecules can bedirectly assessed.

In a light-directed chemical synthesis, the products depend on thepattern of illumination and on the order of addition of reactants. Byvarying the lithographic patterns, many different sets of test compoundscan be synthesized simultaneously; this characteristic leads to thegeneration of many different masking strategies.

E) Encoded Combinatorial Libraries

In yet another embodiment, the subject method utilizes a compoundlibrary provided with an encoded tagging system. A recent improvement inthe identification of active compounds from combinatorial librariesemploys chemical indexing systems using tags that uniquely encode thereaction steps a given bead has undergone and, by inference, thestructure it carries. Conceptually, this approach mimics phage displaylibraries, where activity derives from expressed peptides, but thestructures of the active peptides are deduced from the correspondinggenomic DNA sequence. The first encoding of synthetic combinatoriallibraries employed DNA as the code. A variety of other forms of encodinghave been reported, including encoding with sequenceable bio-oligomers(e.g., oligonucleotides and peptides), and binary encoding withadditional non-sequenceable tags.

1) Tagging with Sequenceable Bio-oligomers

The principle of using oligonucleotides to encode combinatorialsynthetic libraries was described in 1992 (Brenher et al; (1992) PNAS89:5381–5383), and an example of such a library appeared the followingyear (Needles et al. (1993) PNAS 90:10700–10704). A combinatoriallibrary of nominally 7⁷ (=823,543) peptides composed of all combinationsof Arg, Gln, Phe, Lys, Val, D-Val and Thr (three-letter amino acidcode), each of which was encoded by a specific dinucleotide (TA, TC, CT,AT, TT, CA and AC, respectively), was prepared by a series ofalternating rounds of peptide and oligonucleotide synthesis on solidsupport. In this work, the amine linking functionality on the bead wasspecifically differentiated toward peptide or oligonucleotide synthesisby simultaneously preincubating the beads with reagents that generateprotected OH groups for oligonucleotide synthesis and protected NH₂groups for peptide synthesis (here, in a ratio of 1:20). When complete,the tags each consisted of 69-mers, 14 units of which carried the code.The bead-bound library was incubated with a fluorescently labeledantibody, and beads containing bound antibody that fluoresced stronglywere harvested by fluorescence-activated cell sorting (FACS). The DNAtags were amplified by PCR and sequenced, and the predicted peptideswere synthesized. Following such techniques, compound libraries can bederived for use in the subject method, where the oligonucleotidesequence of the tag identifies the sequential combinatorial reactionsthat a particular bead underwent, and therefore provides the identity ofthe compound on the bead.

The use of oligonucleotide tags permits exquisitely sensitive taganalysis. Even so, the method requires careful choice of orthogonal setsof protecting groups required for alternating co-synthesis of the tagand the library member. Furthermore, the chemical lability of the tag,particularly the phosphate and sugar anomeric linkages, may limit thechoice of reagents and conditions that can be employed for the synthesisof non-oligomeric libraries. In preferred embodiments, the librariesemploy linkers permitting selective detachment of the test compoundlibrary member for assay.

Peptides have also been employed as tagging molecules for combinatoriallibraries. Two exemplary approaches are described in the art, both ofwhich employ branched linkers to solid phase upon which coding andligand strands are alternately elaborated. In the first approach (Kerr JM et al. (1993) J Am Chem Soc 115:2529–2531), orthogonality in synthesisis achieved by employing acid-labile protection for the coding strandand base-labile protection for the compound strand.

In an alternative approach (Nikolaiev et al. (1993) Pept Res 6:161–170),branched linkers are employed so that the coding unit and the testcompound can both be attached to the same functional group on the resin.In one embodiment, a cleavable linker can be placed between the branchpoint and the bead so that cleavage releases a molecule containing bothcode and the compound (Ptek et al. (1991) Tetrahedron Lett32:3891–3894). In another embodiment, the cleavable linker can be placedso that the test compound can be selectively separated from the bead,leaving the code behind. This last construct is particularly valuablebecause it permits screening of the test compound without potentialinterference of the coding groups. Examples in the art of independentcleavage and sequencing of peptide library members and theircorresponding tags has confirmed that the tags can accurately predictthe peptide structure.

2) Non-sequenceable Tagging: Binary Encoding

An alternative form of encoding the test compound library employs a setof non-sequencable electrophoric tagging molecules that are used as abinary code (Ohlmeyer et al. (1993) PNAS 90:10922–10926). Exemplary tagsare haloaromatic alkyl ethers that are detectable as theirtrimethylsilyl ethers at less than femtomolar levels by electron capturegas chromatography (ECGC). Variations in the length of the alkyl chain,as well as the nature and position of the aromatic halide substituents,permit the synthesis of at least 40 such tags, which in principle canencode 2⁴⁰ (e.g., upwards of 10¹²) different molecules. In the originalreport (Ohlmeyer et al., supra) the tags were bound to about 1% of theavailable amine groups of a peptide library via a photocleavableo-nitrobenzyl linker. This approach is convenient when preparingcombinatorial libraries of peptide-like or other amine-containingmolecules. A more versatile system has, however, been developed thatpermits encoding of essentially any combinatorial library. Here, thecompound would be attached to the solid support via the photocleavablelinker and the tag is attached through a catechol ether linker viacarbene insertion into the bead matrix (Nestler et al. (1994) J Org Chem59:4723–4724). This orthogonal attachment strategy permits the selectivedetachment of library members for assay in solution and subsequentdecoding by ECGC after oxidative detachment of the tag sets.

Although several amide-linked libraries in the art employ binaryencoding with the electrophoric tags attached to amine groups, attachingthese tags directly to the bead matrix provides far greater versatilityin the structures that can be prepared in encoded combinatoriallibraries. Attached in this way, the tags and their linker are nearly asunreactive as the bead matrix itself. Two binary-encoded combinatoriallibraries have been reported where the electrophoric tags are attacheddirectly to the solid phase (Ohlmeyer et al. (1995) PNAS 92:6027–6031)and provide guidance for generating the subject compound library. Bothlibraries were constructed using an orthogonal attachment strategy inwhich the library member was linked to the solid support by aphotolabile linker and the tags were attached through a linker cleavableonly by vigorous oxidation. Because the library members can berepetitively partially photoeluted from the solid support, librarymembers can be utilized in multiple assays. Successive photoelution alsopermits a very high throughput iterative screening strategy: first,multiple beads are placed in 96-well microtiter plates; second,compounds are partially detached and transferred to assay plates; third,a metal binding assay identifies the active wells; fourth, thecorresponding beads are rearrayed singly into new microtiter plates;fifth, single active compounds are identified; and sixth, the structuresare decoded.

EXEMPLIFICATION

The invention now being generally described, it will be more readilyunderstood by reference to the following examples, which are includedmerely for purposes of illustration of certain aspects and embodimentsof the present invention, and are not intended to limit the invention.

EXAMPLE 1 Synthesis of (3R)-Piperidine-1,3-dicarboxylic acid 1-benzylester 3-ethyl ester (7)

Protocol 1

(R)-Ethyl nipecotate-(l)-tartrate salt (15.0 g, 48.81 mmol) wasdissolved in 61 mL of 3:1 THF:H₂O, and the solution was stirred under N₂at 0° C. 20.24 g (146.4 mmol) of K₂CO₃ was added in one portion, then8.33 mL (51.25 mmol) of (benzyoxy)carbonyl chloride was added dropwise.The reaction was allowed to warm to room temperature with stirringovernight. The solvent was then removed, and EtOAc and H₂O were added.The organic layer was separated, washed with brine, dried with sodiumsulfate, filtered, and concentrated. The crude material was used withoutfurther purification.Protocol 2

A 1.0 L round-bottom flask was charged with K₂CO₃ (29.2 g; 171 mmol),piperidine (50 g; 163 mmol), and a 1:1 mixture of THF/H₂O (800 mL). A150 mL addition funnel was placed on the flask and charged with CbzCl(29.2 g, 171 mmol). The flask was cooled to 0° C. and then CbzCl wasadded dropwise over 5 minutes. The reaction mixture was warmed to 20° C.and stirred for 1 h. The reaction mixture was extracted with EtOAc (500mL) and the organic layer was washed with water (500 mL), saturated NaCl(500 mL), dried (MgSO₄), filtered and concentrated in vacuo. The crudematerial was purified by flash chromatography (silica gel, hexanes/EtOAc9:1 to 4:1) to give pure product (49.3 g, 100% yield). ¹H-NMR (300 MHz)δ (ppm) 7.40 (m; 5H); 5.17 (s; 2H); 4.19 (q; 2H); 4.04 (m; 1H); 3.12 (m;1H); 2.95 (m; 1H); 2.48 (m; 1H); 2.08 (m; 1H); 1.75 (m; 3H); 1.53 (m;1H); 1.28 (t; 3H).

EXAMPLE 2 Synthesis of (3S)-Piperidine-1,3-dicarboxylic acid 1-benzylester 3-ethyl ester (10)

A 1.0 L round-bottom flask was charged with K₂CO₃ (29.2 g; 171 mmol),piperidine (50 g; 163 mmol), and a 1:1 mixture of THF/H₂O (800 mL). A150 mL addition funnel was placed on the flask and charged with CbzCl(29.2 g, 171 mmol). The flask was cooled to 0° C. and then CbzCl wasadded dropwise over 5 minutes. The reaction mixture was warmed to 20° C.and stirred for 1 h. The reaction mixture was extracted with EtOAc (500mL) and the organic layer was washed with water (500 mL), saturated NaCl(500 mL), dried (MgSO₄), filtered and concentrated in vacuo. The crudematerial (49.3 g, 100% yield) was carried on without furtherpurification.

EXAMPLE 3 Synthesis of 3-hydroxymethyl-piperidine-1-carboxylic acidbenzyl ester (8)

Piperidine-1,3-dicarboxylic acid 1-benzyl ester 3-ethyl ester (7) (1.5g, 5.83 mmol) was dissolved in 5.8 mL of anhydrous THF, and the reactionwas stirred under N₂ at −5° C. while lithium aluminum hydride dissolvedin THF (7.0 mL, 1.0M) was added dropwise by addition funnel over 30minutes. When the reaction was complete by TLC (10 min.), H₂O (0.6 mL),then 10% NaOH (1.5 mL), then H₂O (0.6 mL) were added, and the reactionwas stirred for about 45 minutes. The salts were removed by filtrationand the solution was dried with sodium sulfate, filtered, andconcentrated. The crude material was purified using an ISCO CombiFlashflash column (silica, 80:20 Hexane:EtOAc to 40:60 Hexane:EtOAc) toachieve 1.24 g of pure 8 (66% yield).

EXAMPLE 4 Synthesis of (3R)-Piperidine-1,3-dicarboxylic acid 1-benzylester (25)

A 1.0 L round-bottom flask was charged with ester (163 mmol), THF (360mL), MeOH (120 mL), and water (120 mL). The flask was cooled to 0° C.and a solution of LiOH (1.0 M in water, 325 mL; 325 mmol) was addedslowly dropwise. The reaction was stirred overnight at 0° C. and thenquenched with 10% HCl slowly dropwise at 0° C. until the pH˜3. Themixture was extracted with EtOAc (500 mL), washed with water (500 mL),saturated NaCl (500 mL), dried (Na₂SO₄), filtered and concentrated invacuo. The crude material (40.5 g, 95% yield) was carried on withoutfurther purification.

EXAMPLE 5 Synthesis of (3S)-Piperidine-1,3-dicarboxylic acid 1-benzylester (26)

A 1.0 L round-bottom flask was charged with ester (49.3 g, 163 mmol),THF (360 mL), MeOH (120 mL), and water (120 mL) The flask was cooled to0° C. and a solution of LiOH (1.0 M in water; 325 mL; 325 mmol) wasadded slowly dropwise. The reaction was stirred overnight at 0° C. andthen quenched with 10% HCl slowly dropwise at 0° C. until the pH˜3. Themixture was extracted with EtOAc (500 mL), washed with water (500 mL),saturated NaCl (500 mL), dried (Na₂SO₄), filtered and concentrated invacuo. The crude material (39.8 g, 93% yield) was carried on withoutfurther purification.

EXAMPLE 6 Synthesis of (3R)-3-Hydroxymethyl-piperidine-1-carboxylic acidbenzyl ester (8)

A 1.0 L round-bottom flask was charged with acid (40.5 g; 154 mmol) andTHF (600 mL). The reaction mixture was cooled to 0° C. and a 150 mLaddition was charged with borane-dimethyl sulfide (10.0 M neat; 46.2 mL;462 mmol). The borane was added slowly dropwise at 0° C. and thereaction mixture was stirred while warming to 20° C. for 2 hours. Thereaction mixture was cooled to 0° C. and quenched slowly with 10% HCluntil evolution of gas had ceased. The reaction mixture was stirred afurther 30 minutes and then diluted with 10% NaOH (500 mL) and extractedwith EtOAc (500 mL). The organic layer was washed with saturated NaCl(500 mL), dried (Na₂SO₄), filtered and concentrated in vacuo. The crudematerial was purified by flash chromatography (silica gel, hecanes/EtOAc1:1 to 1:2) to give pure product (38.2 g, 100% yield). The enantiomericpurity was 99.16% ee as determined by chiral HPLC analysis. ¹H-NMR (300MHz) δ (ppm) 7.38 (m; 5H); 5.17 (s; 2H); 4.01 (m; 1H); 3.88 (bs; 1H);3.51 (d; 2H); 3.02 (m; 1H); 2.84 (m; 1H); 1.78 (m; 4H); 1.48 (m; 1H);1.23 (m; 1H). ¹³C-NMR (300 MHz) δ (ppm) 155.7; 137.1; 128.7; 128.2;127.9; 67.2; 64.8; 53.9; 47.3; 45.0; 38.7; 27.2; 24.6.

EXAMPLE 7 Synthesis of (3S)-3-Hydroxymethyl-piperidine-1-carboxylic acidbenzyl ester (11)

A 1.0 L round-bottom flask was charged with acid (39.8 g, 151 mmol) andTHF (600 mL). The reaction mixture was cooled to 0° C. and a 150 mLaddition was charged with borane-dimethyl sulfide (10.0 M neat; 45 mL;450 mmol). The borane was added slowly dropwise at 0° C. and thereaction mixture was stirred while warming to 20° C. for 2 hours. Thereaction mixture was cooled to 0° C. and quenched slowly with 10% HCluntil evolution of gas had ceased. The reaction mixture was stirred afurther 30 minutes and then diluted with 10% NaOH (500 mL) and extractedwith EtOAc (500 mL). The organic layer was washed with saturated NaCl(500 mL), dried (Na₂SO₄), filtered and concentrated in vacuo. The crudematerial was purified by flash chromatography (silica gel, hexanes/EtOAc1:1 to 1:2) to give pure product (36.0 g, 96% yield). The enantiomericpurity was 99.58% ee as determined by chiral HPLC analysis. ¹H-NMR (300MHz) δ (ppm) 7.40 (m; 5H); 5.14 (s; 2H); 4.01 (m; 1H); 3.86 (bs; 1H);3.50 (d; 2H); 3.11 (m; 1H); 2.76 (m; 1H); 1.75 (m; 4H); 1.43 (m; 1H);1.25 (m; 1H).

EXAMPLE 8 Synthesis of 3-formyl-piperidine-1-carboxylic acid benzylester (9)

To a stirring, 0° C. solution of 0.303 g (1.20 mmol) of3-hydroxymethyl-piperidine-1-carboxylic acid benzyl ester (8) in CH₂Cl₂(4.0 mL) was added 0.630 g (1.44 mmol) of Dess-Martin periodinane, andthe solution was stirred under N₂. When the reaction was complete by TLC(about 30 min.), the reaction was concentrated, and then Et₂O was added.After standing for about 15 min., the reaction was filtered throughCelite wet with Et₂O, rinsed with Et₂O, and concentrated. The crudereaction was purified by column chromatography (florisil®, 100–200 mesh,2:1 Hexane:EtOAc) to achieve pure 9.

EXAMPLE 9 Synthesis of (3R)-Formyl-piperidine-1-carboxylic acid benzylester (8)

A 500 mL RB flask was charged with DCM (300 mL) and oxalyl chloride (5.8mL; 66 mmol) and then cooled to −78° C. A 150 mL addition funnel wascharged with DMSO (8.5 mL; 120 mmol) and DCM (30 mL). The DMSO was addedslowly dropwise at −78° C. and the reaction mixture was stirred for 30min. The 150 mL addition funnel was charged with alcohol (16.5 g; 60mmol) and DCM (30 mL). The alcohol was added slowly dropwise at −78° C.and the reaction mixture was stirred for 10 min. The 150 mL additionfunnel was charged with triethyl amine (42 mL; 300 mmol). The amine wasadded slowly dropwise at −78° C. and the reaction mixture was stirredwhile warming to 0° C. for 30 min. The reaction mixture was quenchedwith water (500 mL) and extracted with DCM (500 mL). The organic layerwas washed with 1.0 M NaHSO₄ (500 mL), dried (Na₂SO₄), filtered andconcentrated in vacuo. The crude material was purified by flashchromatography (florosil, hexanes/EtOAc 2:1) to give pure product (15.1g, 100% yield). Note: The aldehyde was either used immediately in thenext step or stored at −20° C. under an argon atmosphere. ¹H-NMR (300MHz) δ (ppm) 9.72 (s; 1H); 7.38 (m; 5H); 5.17 (s; 2H); 4.05 (m; 1H);3.79 (m; 1H); 3.41 (dd; 1H); 3.19 (m; 1H); 2.48 (m; 1H); 2.02 (m; 1H);1.73 (m; 2H); 1.58 (m; 1H).

EXAMPLE 10 Synthesis of (3S)-Formyl-piperidine-1-carboxylic acid benzylester (12)

A 250 mL RB flask was charged with DCM (100 mL) and oxalyl chloride(2.31 mL; 26.4 mmol) and then cooled to −78° C. A 25 mL addition funnelwas charged with DMSO (3.42 mL; 48.2 mmol in 15 mL DCM). The DMSO wasadded slowly dropwise at −78° C. and the reaction mixture was stirredfor 30 min. The 25 mL addition funnel was charged with alcohol (6.0 g;24.1 mmol in 15 mL DCM. The alcohol was added slowly dropwise at −78° C.and the reaction mixture was stirred for 10 min. The 25 mL additionfunnel was charged with triethyl amine (16.8 mL; 120 mmol). The aminewas added slowly dropwise at −78° C. and the reaction mixture wasstirred while warming to 0° C. for 30 min. The reaction mixture wasquenched with water (200 mL) and extracted with DCM (100 mL). Theorganic layer was washed with 1.0 M NaHSO₄ (250 mL), dried (Na₂SO₄),filtered and concentrated in vacuo. The crude material was purified byflash chromatography (florosil, hexanes/EtOAc 2:1) to give pure product(5.53 g, 92.7% yield). The aldehyde was either used immediately in thenext step or stored at −20° C. under an argon atmosphere. ¹H-NMR (300MHz) δ (ppm) 9.74 (5; 1H); 7.37 (m; 5H); 5.15 (s; 2H); 4.08 (m; 1H);3.76 (m; 1H); 3.41 (dd; 1H); 3.17 (m; 1H); 2.46 (m; 1H); 2.02 (m; 1H);1.73 (m; 2H); 1.58 (m; 1H).

EXAMPLE 11 Synthesis of 2-napthyl TADDOL catalyst (13)

Protocol 1

Using Schlenck glassware and air-free conditions, freshly distilledtitanium tetraisopropoxide (0.079 mL, 0.267 mmol) was added to(4R-trans)-2,2-Dimethyl-α,α,α′,α′-tetra-(2-napthyl)-1,3-dioxolane-4,5-dimethanol(0.162 g, 0.243 mmol) in anhydrous toluene freshly distilled fromsodium/benzophenone (2.21 mL), and the reaction was stirred at 40° C.for 5 hours. The reaction was then concentrated in vacuo, stored underargon until it was used without further purification.Protocol 2

A flame dried 200 mL round-bottom flask was purged with argon and thencharged with 4R-diol (4.04 g; 6.1 mmol), toluene (60 mL; pre-dried with4 Å molecular sieves) and titanium (IV) isopropoxide (1.79 mL; 6.1mmol). The reaction mixture was heated to 50° C. and stirred for 4 hunder an argon atmosphere. The toluene was removed in vacuo to give thecatalyst as a pale yellow solid. The catalyst was kept under vacuum andthen used immediately after purging with argon.Protocol 3

A flame dried 200 mL round-bottom flask was purged with argon and thencharged with 4R-diol (2.02 g; 3.0 mmol), toluene (30 mL; pre-dried with4 Å molecular sieves) and titanium (IV) isopropoxide (0.90 mL; 3.0mmol). The reaction mixture was heated to 50° C. and stirred for 5 hunder an argon atmosphere. The toluene was removed in vacuo to give thecatalyst as a pale yellow solid. The catalyst was kept under vacuum andthen used immediately after purging with argon.

EXAMPLE 12 Synthesis of (R,S)-3-(1-Hydroxyethyl)-piperidine-1-carboxylicacid benzyl ester (15)

Protocol 1

Using Schlenck glassware and air-free conditions, anhydrous ethyl etherfreshly distilled from sodium/benzophenone (2.43 mL) was added tocatalyst 13 prepared according to Example 11, protocol 1. Freshlydistilled titanium tetraisopropoxide (0.430 mL, 1.46 mmol) was added,and the reaction was cooled to −78° C. Commercial Me₂Zn (1.21 mL, 2 M intoluene) was added, and the reaction was stirred at −78° C. for 1 hour.Aldehyde 9 (0.300 g, 1.21 mmol) in Et₂O (0.3 mL) was added, and thereaction was warmed to −30° C. and stirred overnight. The reaction wasthen quenched at −30° C. with saturated aqueous NH₄Cl. Et₂O was added,and the reaction was filtered through Celite wet with Et₂O. The reactionwas dried with sodium sulfate, filtered, concentrated, and purifiedusing an ISCO CombiFlash column (silica, 2:1 Hexane:EtOAc) to obtain 15(0.162 g, 51%). HLPC analysis of the product presented in the Figures.¹H NMR (CDCl₃, 300 MHz) 7.43–7.31 (5H, broad s), 5.16 (2H, s), 4.30–3.60(2H, broad m), 3.63 (1H, dq, J=6.4, 6.4 Hz), 3.30–2.70 (2H, broad s),2.15–1.90 (1H, broad s), 1.84–1.72 (1H, m), 1.76–1.56 (1H, m), 1.58–1.36(2H, m), 1.23 (3H, d, J=6.4 Hz) ppm. ¹³C NMR (CDCl₃, 75 MHz) 155.81,137.04, 128.61, 128.08, 127.93, 68.35, 67.19, 46.61, 45.02, 43.25,27.08, 24.37, 20.95 ppm. LRMS m/z 263.68 (M⁺, C₁₅H₂₁NO₃, requires263.15.Protocol 2

A 200 mL round-bottom flask containing 4R-TADDOL (6.12 mmol) was chargedwith anhydrous ether (80 mL) and titanium isopropoxide (14.3 mL; 49mmol). The solution was cooled to −78° C. and a 2.0 M solution ofdimethyl zinc (40.5 mL; 81 mmol) was added. The solution was stirred at−78° C. for 1 h. To the solution was added aldehyde (10.0 g; 40.4 mmol)dissolved in ether (10 mL). The reaction mixture was warmed to −30° C.and stirred for 72 h. The reaction mixture was diluted with ether (500mL) and quenched by the slow addition of saturated NH₄Cl (10 mL). Theslurry was stirred at 20° C. for 10 min and then filtered throughcelite. The celite pad was washed with ether and the combined organiclayers were concentrated in vacuo. The crude material was purified byflash chromatography (silica gel, hexanes/EtOAc 2:1 to 1:1) to givefirst, recovered 4R-ligand (3.62 g; 90% recovery) and second, pureproduct (6.51 g, 61% yield). The diastereomeric purity was 90.2% de asdetermined by achiral HPLC analysis. The enantiomeric purity of themajor diastereomer was 99.8% ee as determined by chiral HPLC analysis.¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 5.17 (s; 2H); 4.20 (m; 1H); 3.98(m; 2H); 3.77 (m; 1H); 3.51 (m; 1H); 3.18 (m; 1H; 2.87 (m; 1H); 1.80 (m;1H); 1.68 (m; 1H); 1.48 (m; 2H); 1.23 (d; 3H). ¹³C-NMR (300 MHz) δ (ppm)155.8; 137.2; 128.7; 128.1; 128.0; 68.8; 67.2; 46.8; 45.0; 43.5; 27.2;24.8; 21.1.

EXAMPLE 13 Synthesis of(3R)-3-((1S)-1-Hydroxy-ethyl)-piperidine-1-carboxylic acid benzyl ester(15) using catalyst (13) obtained from recycled diol ligand

The 4R-Ligand recovered from the column chromatography can be used againwithout any loss in yield (75% yield) or diastereoselectivity (90.3%d.e.) of 15.

EXAMPLE 14 Synthesis of(3S)-3-((1S)-1-Hydroxy-ethyl)-piperidine-1-carboxylic acid benzyl ester(27)

A 200 mL round-bottom flask containing 4R-TADDOL (3.0 mmol) was chargedwith anhydrous ether (40 mL) and titanium isopropoxide (7.16 mL; 24.5mmol). The solution was cooled to −78° C. and a 2.0 M solution ofdimethyl zinc (20.2 mL; 40.5 mmol) was added. The solution was stirredat −78° C. for 1 h. To the solution was added aldehyde (5.0 g; 20.2mmol) dissolved in ether (2.5 mL). The reaction mixture was warmed to−30° C. and stirred for 72 h. The reaction mixture was diluted withether (250 mL) and quenched by the slow addition of saturated NH₄Cl (5mL). The slurry was stirred at 20° C. for 10 min and then filteredthrough celite. The celite pad was washed with ether and the combinedorganic layers were concentrated in vacuo. The crude material waspurified by flash chromatography (silica gel, hexanes/EtOAc 2:1 to 1:1)pure product (3.15 g, 59% yield). The diastereomeric purity was 89.22%de as determined by achiral HPLC analysis. The enantiomeric purity ofthe major diastereomer was >98.9% ee as determined by chiral HPLCanalysis. ¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 5.17 (s; 2H); 4.10 (m;2H); 3.66 (m; 1H); 2.82 (m; 1H); 2.76 (m; 1H); 1.98 (m; 2H); 1.75 (m;1H); 1.48 (m; 2H); 1.30 (m; 1H); 1.22 (d; 3H). ¹³C-NMR (300 MHz) δ (ppm)155.7; 137.1; 128.7; 128.2; 128.0; 69.4; 67.3; 47.1; 44.9; 43.3; 25.8;24.9; 21.1.

EXAMPLE 15 Synthesis of 2-napthyl TADDOL catalyst (14)

Protocol 1

Using Schlenck glassware and air-free conditions, freshly distilledtitanium tetraisopropoxide (0.079 mL, 0.267 mmol) was added to(4S-trans)-2,2-Dimethyl-α,α,α′,α′-tetra-(2-napthyl)-1,3-dioxolane-4,5-dimethanol(0.162 g, 0.243 mmol) in anhydrous toluene freshly distilled fromsodium/benzophenone (2.21 mL), and the reaction was stirred at 40° C.for 5 hours. The reaction was then concentrated in vacuo, stored underargon until it was used without further purification.Protocol 2

A flame dried 200 mL round-bottom flask was purged with argon and thencharged with 4S-diol (4.04 g; 6.1 mmol), toluene (60 mL; pre-dried with4 Å molecular sieves) and titanium (IV) isopropoxide (1.79 mL; 6.1mmol). The reaction mixture was heated to 50° C. and stirred for 4 hunder an argon atmosphere. The toluene was removed in vacuo to give thecatalyst as a pale yellow solid. The catalyst was kept under vacuum andthen used immediately after purging with argon.Protocol 3

A flame dried 200 mL round-bottom flask was purged with argon and thencharged with 4S-diol (2.02 g; 3.0 mmol), toluene (30 mL; pre-dried with4 Å molecular sieves) and titanium (IV) isopropoxide (0.90 mL; 3.0mmol). The reaction mixture was heated to 50° C. and stirred for 5 hunder an argon atmosphere. The toluene was removed in vacuo to give thecatalyst as a pale yellow solid. The catalyst was kept under vacuum andthen used immediately after purging with argon.

EXAMPLE 16 Synthesis of (R,R)-3-(1-Hydroxyethyl)-piperidine-1-carboxylicacid benzyl ester (16)

Protocol 1

Using Schlenck glassware and air-free conditions, anhydrous ethyl etherfreshly distilled from sodium/benzophenone (2.43 mL) was added tocatalyst 14 prepared according to Example 15, protocol 1. Freshlydistilled titanium tetraisopropoxide (0.430 mL, 1.46 mmol) was added,and the reaction was cooled to −78° C. Commercial Me₂Zn (1.21 mL, 2 M intoluene) was added, and the reaction was stirred at −78° C. for 1 hour.Aldehyde 9 (0.300 g, 1.21 mmol) in Et₂O (0.3 mL) was added, and thereaction was warmed to −30° C. and stirred overnight. The reaction wasthen quenched at −30° C. with saturated aqueous NH₄Cl. Et₂O was added,and the reaction was filtered through Celite wet with Et₂O. The reactionwas dried with sodium sulfate, filtered, concentrated, and purifiedusing an ISCO CombiFlash column (silica, 2:1 Hexane:EtOAc) to obtain 16(0.167 g, 52%). HLPC analysis of the product is depicted in the Figures.¹H NMR (CDCl₃, 300 MHz) 7.42–7.30 (5H, broad s), 5.15 (2H, s), 4.08 (2H,broad d, J=12.8 Hz), 3.67 (1H, dq, J=6.2, 6.2 Hz), 2.81 (1H, td, J=12.4,3.1 Hz), 3.90–2.60 (1H, broad), 2.40–1.90 (2H, broad), 1.80–1.68 (1H,m), 1.56–1.40 (2H, m), 1.23 (3H, d, J=6.3 Hz) ppm. ¹³C NMR (CDCl₃, 75MHz) 155.58, 137.06, 128.61, 128.07, 127.91, 69.38, 67.14, 46.94, 44.81,43.14, 25.71, 24.95, 21.03 ppm.Protocol 2

A 200 mL round-bottom flask containing 4S-TADDOL (14) (6.12 mmol) wascharged with anhydrous ether (80 mL) and titanium isopropoxide (14.3 mL;49 mmol). The solution was cooled to −78° C. and a 2.0 M solution ofdimethyl zinc (40.5 mL; 81 mmol) was added. The solution was stirred at−78° C. for 1 h. To the solution was added aldehyde (10.6 g; 42.5 mmol)dissolved in ether (10 mL). The reaction mixture was warmed to −30° C.and stirred for 72 h. The reaction mixture was diluted with ether (500mL) and quenched by the slow addition of saturated NH₄Cl (10 mL). Theslurry was stirred at 20° C. for 10 min and then filtered throughcelite. The celite pad was washed with ether and the combined organiclayers were concentrated in vacuo. The crude material was purified byflash chromatography (silica gel, hexanes/EtOAc 2:1 to 1:1) to give pureproduct (6.95 g, 62% yield). The diastereomeric purity was 90.1% de asdetermined by achiral HPLC analysis. The enantiomeric purity of themajor diastereomer was >99.0% ee as determined by chiral HPLC analysis.¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 5.17 (s; 2H); 4.06 (m; 2H); 3.65(m; 1H); 2.81 (m; 1H); 2.76 (m; 1H); 1.98 (m; 2H); 1.75 (m; 1H); 1.48(m; 2H); 1.30 (m; 1H); 1.21 (d; 3H). ¹³C-NMR (300 MHz) δ (ppm) 155.7;137.1; 128.7; 128.2; 128.0; 69.2; 67.3; 47.1; 44.9; 43.3; 25.9; 25.2;21.0.

EXAMPLE 17 Synthesis of(3S)-3-((1R)-1-Hydroxy-ethyl)-piperidine-1-carboxylic acid benzyl ester(28)

A 200 mL round-bottom flask containing 4S-TADDOL (14, 3.0 mmol) wascharged with anhydrous ether (40 mL) and titanium isopropoxide (7.16 mL;24.5 mmol). The solution was cooled to −78° C. and a 2.0 M solution ofdimethyl zinc (20.2 mL; 40.5 mmol) was added. The solution was stirredat −78° C. for 1 h. To the solution was added aldehyde (5.0 g; 20.2mmol) dissolved in ether (2.5 mL). The reaction mixture was warmed to−30° C. and stirred for 72 h. The reaction mixture was diluted withether (250 mL) and quenched by the slow addition of saturated NH₄Cl (5mL). The slurry was stirred at 20° C. for 10 min and then filteredthrough celite. The celite pad was washed with ether and the combinedorganic layers were concentrated in vacuo. The crude material waspurified by flash chromatography (silica gel, hexanes/EtOAc 2:1 to 1:1)to give pure product (3.6 g, 67% yield). The diastereomeric purity was94.9% de as determined by achiral HPLC analysis. The enantiomeric purityof the major diastereomer was >99.0% ee as determined by chiral HPLCanalysis. ¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 5.14(s; 2H); 4.17 (m;1H); 3.99 (m; 2H); 3.77 (m; 1H); 3.58 (m; 1H); 3.18 (m; 1H; 2.87 (m;1H); 1.80 (m; 1H); 1.65 (m; 1H); 1.48 (m; 2H); 1.23 (d; 3H). ¹³C-NMR(300 MHz) δ (ppm) 155.9; 137.2; 128.7; 128.2; 128.0; 68.4; 67.3; 46.7;45.1; 43.3; 27.2; 24.5; 21.1.

EXAMPLE 18

The chromatographic conditions used to separate the four isomers, 15,16, 27 and 28, are described below. The chromatographic conditionsgenerated the chromatographic separation depicted in FIG. 11.

Column: Chiralpak AD, 5 um, 4.6×250 mm

Mobile Phase: Hexane/IPA (97:3)

Flow Rate: 1.5 mL/min

Detection: UV 210 nm

Temperature: 5° C.

Identification of each peak was determined using authentic samples ofeach stereoisomer of 3-(1-hydroxyethyl)piperidine-1-carboxylic acidbenzyl ester. This chiral HPLC method was subsequently used to analyzeseveral samples of individual isomers. Representative chromatograms foreach of the samples are presented in FIGS. 12–15.

Using peak area normalization to quantify the amount of individualisomers in each sample, the following data were obtained.

% (R,R)- % (S,S)- % (R,S)- % (S,R)- % de % ee Isomer Isomer IsomerIsomer major major Sample 16 27 15 28 isomer isomer Example 12  1.23 3.02 95.65 0.11 91.3  99.8 (Protocol 2) Example 14 <0.5%, ND 94.61 1.13 4.26 89.2 >98.9 Example 16 96.17 <0.5%, ND  2.30 1.53 92.3 >99.0(Protocol 2) Example 17  1.22  1.28 <0.5%, ND 97.50  95.0 >99.0 ND =None Detected.

Since there was insufficient sample available to perform a spikedrecovery study, the detection limit for the minor isomers in thepresence of the major isomer was estimated at approximately 0.5%. In thecase of Example 12, (R,S)-Isomer, there was a trace of the minor(S,R)-Isomer observed in the sample, and the integration determined itto be 0.11%.

EXAMPLE 19 Non-selective Synthesis of a Mixture of 15 and 16

MeMgI (0.80 mL, 3.0M in Et₂O) was added dropwise to a stirring, −78° C.solution of aldehyde 9 (0.313 g, 1.20 mmol) in THF (6.0 mL). When thereaction was complete by TLC, the reaction was quenched with aqueousNH₄Cl, washed with H₂O, and extracted with EtOAc. The crude reactionmixture was dried with sodium sulfate and purified using an ISCOCombiFlash column (silica, 2:1 Hexane:EtOAc). HPLC analysis of theproduct is depicted in the Figures.

EXAMPLE 20 Testing Reaction Conditions for the Conversion of 9 to 15Catalyzed by Catalyst 13

Using Schlenck glassware and air-free conditions, ethyl ether (2.12 mL)was added to catalyst 13. Catalyst 13 had been prepared either fromtoluene freshly distilled from sodium/benzophenone under argon, or ithad been prepared from anhydrous toluene purchased from Aldrich andpre-dried for 24 hours with 4 Å molecular sieves that had been heated ina vacuum oven for 24 hours prior to their use. The amount of catalyst 13was 5 mol %, 10 mol %, or 20 mol %. The ether solvent was either freshlydistilled from sodium/benzophenone under argon, or was anhydrous etherpurchased from Aldrich and pre-dried for 24 hours with 4 Å molecularsieves that had been heated in a vacuum oven for 24 hours prior to theiruse. Titanium tetraisopropoxide (0.347 mL, 1.27 mmol) was added, and thereaction was cooled to −78° C. Commercial Me₂Zn (1.06 mL, 2 M intoluene) was added, and the reaction was stirred at −78° C. for 1 hour.Aldehyde 9 (0.262 g, 1.06 mmol) in Et₂O (0.2 mL) was added, and thereaction was warmed to −30° C. and stirred overnight. The reaction wasthen quenched at −30° C. with saturated aqueous NH₄Cl. Et₂O was added,and the reaction was filtered through Celite wet with Et₂O. The reactionwas dried with sodium sulfate, filtered, concentrated, and purifiedusing an ISCO CombiFlash column (silica, 2:1 Hexane:EtOAc) to obtain 15.HLPC analysis of the results of these reactions is depicted in theFigures.

EXAMPLE 21 Synthesis of 3-(1-phenylaminoethyl)piperidine-1-carboxylicacid tert-butyl ester 22

To a stirred suspension of 3-(1-hydroxyethyl)piperidine-1-carboxylicacid tert-butyl ester 21 (31 mg, 0.135 mmol) and piperidinomethylpolystyrene resin (60 mg) in 0.5 mL of CH₂Cl₂ was added methanesulfonylchloride (15.7 μL, 1.5 eq.). The mixture was stirred at room temperaturefor 60 min. After removal of solvent, aniline (50 μL) was introduced.The mixture was heated at 95° C. overnight. The crude product waspurified by a preparative thin layer chromatography (EtOAc/Hexane, 1:2)to afford 3-(1-phenylaminoethyl)piperidine-1-carboxylic acid tert-butylester 22 (21 mg, 51%).

EXAMPLE 22 Synthesis of(3R)-3-((1S)-1-Methanesulfonyloxy-ethyl)-piperidine-1-carboxylic acidbenzyl ester (29)

A 200 mL round-bottom flask was charged with alcohol (7.19 g; 27.3mmol), DCM (100 mL) and diisopropylethylamine (5.23 mL; 30.0 mmol). Theflask was cooled to 0° C. and methanesulfonyl chloride (2.32 mL; 30.0mmol) was added dropwise. The reaction was warmed to 20° C. and stirredfor 2 h. The reaction mixture was diluted with DCM (150 mL). The organiclayer was washed with saturated NaHCO₃ (250 mL), saturated NaCl (250mL), dried (Na₂SO₄), filtered and concentrated in vacuo. The crudematerial was purified by flash chromatography (silica gel, hexanes/EtOAc4:1 to 2:1 with 2% 2.0 M NH₃ in EtOH) to give pure product (8.76 g, 94%yield). ¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 5.17 (s; 2H); 4.71 (m;1H); 4.25 (m; 1H); 4.08 (m; 1H); 3.02 (m; 2H); 2;89 (bs: 3H); 2.76 (m;1H); 1.85 (m; 1H); 1.78 (m; 2H); 1.48 (d; 3H); 1.21 (m; 1H). ¹³C-NMR(300 MHz) δ (ppm) 155.5; 137.0; 128.8; 128.2; 128.0; 81.0; 67.3; 45.8;44.6; 41.4; 38.8; 27.0; 24.8; 19.2.

EXAMPLE 23 Synthesis of(3R)-3-((1R)-1-Methanesulfonyloxy-ethyl)-piperidine-1-carboxylic acidbenzyl ester (30)

A 200 mL round-bottom flask was charged with alcohol (3.15 g; 12.0mmol), DCM (100 mL) and diisopropylethylamine (2.29 mL; 13.2 mmol). Theflask was cooled to 0° C. and methanesulfonyl chloride (1.02 mL; 13.2mmol) was added dropwise. The reaction was warmed to 20° C. and stirredfor 2 h. The reaction mixture was diluted with DCM (150 mL). The organiclayer was washed with saturated NaHCO₃ (250 mL), saturated NaCl (250mL), dried (Na₂SO₄), filtered and concentrated in vacuo. The crudematerial was purified by flash chromatography (silica gel, hexanes/EtOAc4:1 to 2:1 with 2% 2.0 M NH₃ in EtOH) to give pure product (3.92 g, 96%yield). ¹H-NMR (300 MHz) δ (ppm) 7.40 (m; 5H); 5.19 (s; 2H); 4.75 (m;1H); 4.16 (m; 2H); 3.02 (bs; 3H); 2.82 (m: 2H); 1.99 (m; 1H); 1.78 (m;2H); 1.42 (d; 3H); 1.39 (m; 2H). ¹³C-NMR (300 MHz) δ (ppm) 155.4; 137.0;128.8; 128.3; 128.0; 80.8; 67.3; 46.2; 44.7; 41.4; 39.0; 26.0; 24.7;18.9.

EXAMPLE 24 Synthesis of(3S)-3-((1S)-1-Methanesulfonyloxy-ethyl)-piperidine-1-carboxylic acidbenzyl ester (31)

A 200 mL round-bottom flask was charged with alcohol (0.5 g; 1.9 mmol),DCM (10 mL) and diisopropylethylamine (0.4 mL; 2.09 mmol). The flask wascooled to 0° C. and methanesulfonyl chloride (0.16 mL; 2.09 mmol) wasadded dropwise. The reaction was warmed to 20° C. and stirred for 2 h.The reaction mixture was diluted with DCM (15 mL). The organic layer waswashed with saturated NaHCO₃ (25 mL), saturated NaCl (25 mL), dried(Na₂SO₄), filtered and concentrated in vacuo. The crude material waspurified by flash chromatography (silica gel, hexanes/EtOAc 4:1 to 2:1with 2% 2.0 M NH₃ in EtOH) to give pure product (616 g, 95% yield).¹H-NMR (300 MHz) δ (ppm) 7.40 (m; 5H); 5.19 (s; 2H); 4.75 (m; 1H); 4.16(m; 2H); 3.02 (bs; 3H); 2.82 (m: 2H); 1.99 (m; 1H); 1.78 (m; 2H); 1.42(d; 3H); 1.39 (m; 2H). ¹³C-NMR (300 MHz) δ (ppm) 155.3; 137.1; 128.7;128.2; 128.0; 80.7; 67.2; 46.2; 44.7; 41.4; 38.8; 25.9; 24.6; 18.8.

EXAMPLE 25 Synthesis of(3S)-3-((1R)-1-Methanesulfonyloxy-ethyl)-piperidine-1-carboxylic acidbenzyl ester (32)

A 200 mL round-bottom flask was charged with alcohol (0.5 g; 1.9 mmol),DCM (10 mL) and diisopropylethylamine (0.4 mL; 2.09 mmol). The flask wascooled to 0° C. and methanesulfonyl chloride (0.16 mL; 2.09 mmol) wasadded dropwise. The reaction was warmed to 20° C. and stirred for 2 h.The reaction mixture was diluted with DCM (15 mL). The organic layer waswashed with saturated NaHCO₃ (25 mL), saturated NaCl (25 mL), dried(Na₂SO₄), filtered and concentrated in vacuo. The crude material waspurified by flash chromatography (silica gel, hexanes/EtOAc 4:1 to 2:1with 2% 2.0 M NH₃ in EtOH) to give pure product (0.596 g, 92% yield).¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 5.17 (s; 2H); 4.71 (m; 1H); 4.25(m; 1H); 4.08 (m; 1H); 3.02 (m; 2H); 2;89 (bs: 3H); 2.76 (m; 1H); 1.85(m; 1H); 1.78 (m; 2H); 1.48 (d; 3H); 1.21 (m; 1H). ¹³C-NMR (300 MHz) δ(ppm) 155.5; 137.0; 128.8; 128.2; 128.0; 81.0; 67.3; 45.8; 44.6; 41.4;38.8; 27.0; 24.8; 19.2.

EXAMPLE 26 Synthesis of(3R)-3-((1R)-1-Phenylamino-ethyl)-piperidine-1-carboxylic acid benzylester (17)

A 100 mL par-shaker flask was charged with mesylate (6.95 g, 20.4 mmol)and aniline (55 mL; 611 mmol). The reaction mixture was sealed andheated to 95° C. for 48 h. The excess aniline was removed by vacuumdistillation and the crude material was purified by flash chromatography(silica gel, hexanes/EtOAc 19:1 to 4:1 with 2% 2.0 M NH₃ in EtOH) togive product (7.52 g, >100% yield). The crude product was contaminatedby aniline that could not be completely removed by additional columnchromatography. The diastereomeric purity was 90.6% de as determined byHPLC analysis. ¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H); 7.20 (t; 2H); 6.77(t; 1H); 6.61 (d; 2H); 5.17 (s; 2H): 4.15 (m; 2H); 3.40 (m; 2H); 2.85(m; 2H); 2.00 (m; 1H); 1.88 (m; 1H); 1.63 (m; 1H); 1.50 (m; 1H); 1.30(m; 1H); 1.21 (d; 3H). ¹³C-NMR (300 MHz) δ (ppm) 155.7; 148.0; 137.3;129.7; 128.8; 128.3; 128.1; 117.3; 113.4; 67.3; 51.1; 47.4; 45.0; 42.1;27.5; 25.4; 18.5.

EXAMPLE 27 Synthesis of(3R)-3-((1S)-1-Phenylamino-ethyl)-piperidine-1-carboxylic acid benzylester (19)

A 100 mL par-shaker flask was charged with mesylate (3.92 g, 11.5 mmol)and aniline (31 mL; 344 mmol). The reaction mixture was sealed andheated to 95° C. for 48 h. The excess aniline was removed by vacuumdistillation and the crude material was purified by flash chromatography(silica gel, hexanes/EtOAc 19:1 to 4:1 with 2% 2.0 M NH₃ in EtOH) togive product (4.09 g, >100% crude yield). The crude product wascontaminated by aniline that could not be completely removed byadditional column chromatography. ¹H-NMR (300 MHz) δ (ppm) 7.38 (m; 5H);7.20 (t; 2H); 6.77 (t; 2H); 6.61 (d; 1H); 5.17 (s; 2H): 4.40 (m; 1H);4.18 (m; 1H); 3.39 (m; 1H); 2.80 (m; 2H); 2.58 (m; 1H); 1.92 (m; 1H);1.78 (m; 1H); 1.53 (m; 2H); 1.28 (m; 1H); 1.19 (d; 3H). ¹³C-NMR (300MHz) δ (ppm) 155.7; 148.0; 137.4; 129.8; 128.9; 128.3; 128.2; 117.4;113.6; 67.4; 51.2; 48.1; 45.1; 42.1; 27.5; 25.8; 18.3.

EXAMPLE 28 Synthesis of(3S)-3-((1R)-1-Phenylamino-ethyl)-piperidine-1-carboxylic acid benzylester (33)

A 100 mL par-shaker flask was charged with mesylate (0.3 g, 0.88 mmol)and aniline (5 mL; 55.5 mmol). The reaction mixture was sealed andheated to 90° C. for 48 h. The excess aniline was removed by vacuumdistillation and the crude material was purified by flash chromatography(silica gel, hexanes/EtOAc 19:1 to 4:1 with 2% 2.0 M NH₃ in EtOH) togive product (0.272 g, 91% yield). The diastereomeric purity was 84.36%de as determined by HPLC analysis. ¹H-NMR (300 MHz) δ (ppm) 7.37 (m;5H); 7.20 (t; 2H); 6.70 (t; 2H); 6.61 (d; 1H); 5.15 (s; 2H): 4.40 (m;1H); 4.15 (m; 1h); 3.40 (m; 1H); 2.78 (m; 2H); 2.52 (m; 1H); 1.92 (m;1H); 1.78 (m; 1H); 1.53 (m; 2H); 1.28 (m; 1H); 1.19 (d; 3H). ¹³C-NMR(300 MHz) δ (ppm) 155.6; 147.8; 137.3; 129.6; 128.9; 128.2; 128.1;117.4; 113.5; 67.3; 51.0; 48.0; 45.0; 42.1; 27.4; 25.6; 18.2.

The lower % de observed for this reaction reflects the % de of thestarting alcohol (27), and not of a lack of stereochemical integrity forthis reaction. Alcohol 27 was synthesized from aldehyde 12 that had beenstored at room temperature. Storage of the aldehyde at room temperatureresults in reduced enantiopurity.

EXAMPLE 29 Synthesis of(3S)-3-((1S)-1-Phenylamino-ethyl)-piperidine-1-carboxylic acid benzylester (34)

A 100 mL par-shaker flask was charged with mesylate (0.45 g, 1.32 mmol)and aniline (7.5 mL; 83.25 mmol). The reaction mixture was sealed andheated to 90° C. for 48 h. The excess aniline was removed by vacuumdistillation and the crude material was purified by flash chromatography(silica gel, hexanes/EtOAc 19:1 to 4:1 with 2% 2.0 M NH₃ in EtOH) togive product (0.381 g, 85% yield). The diastereomeric purity was 92.86%de as determined by HPLC analysis. ¹H-NMR (300 MHz) δ (ppm) 7.38 (m;5H); 7.20 (t; 2H); 6.77 (t; 1H); 6.61 (d; 2H); 5.17 (s; 2H): 4.15 (m;2H); 3.40 (m; 2H); 2.85 (m; 2H); 2.00 (m; 1H); 1.88 (m; 1H); 1.63 (m;1H); 1.50 (m; 1H); 1.30 (m; 1H); 1.21 (d; 3H). ¹³C-NMR (300 MHz) δ (ppm)155.7; 148.0; 137.3; 129.7; 128.8; 128.3; 128.1; 117.3; 113.4; 67.3;51.1; 47.4; 45.0; 42.1; 27.5; 25.4; 18.5.

EXAMPLE 30 Synthesis of(3R)-3-((1R)-1-Phenylamino-ethyl)-piperidine-1-carboxylic acid benzylester (17)

A 50 mL round-bottom flask was charged with alcohol (1.0 g, 3.80 mmol),DCM (5 mL) and 2,6-lutidine (487 μL; 4.20 mol). The reaction mixture wascooled to −78° C. and Tf₂O (703 μL ; 4.18 mmol) was added dropwise. Thereaction mixture was stirred at −78° C. for 1 h. To the reaction mixturewas added aniline (519 mL; 5.70 μmol) and 2,6-lutidine (663 μL; 5.70mmol). The reaction mixture was warmed to 0° C. and stirred for 2 h. Thereaction mixture was diluted with DCM (50 mL), washed with saturatedNaHCO₃ (50 mL), saturated NaCl (50 mL), dried (Na₂SO₄), filtered andconcentrated in vacuo. The crude material was purified by flashchromatography (silica gel, hexanes/EtOAc 19:1 to 4:1 with 2% 2.0 M NH₃in EtOH) to give product (720 mg, 56% yield). ¹H-NMR (300 MHz) δ (ppm)7.38 (m; 5H); 7.20 (t; 2H); 6.77 (t; 1H); 6.61 (d; 2H); 5.17 (s; 2H):4.15 (m; 2H); 3.40 (m; 2H); 2.85 (m; 2H); 2.00 (m; 1H); 1.88 (m; 1H);1.63 (m; 1H); 1.50 (m; 1H); 1.30 (m; 1H); 1.21 (d; 3H). ¹³C-NMR (300MHz) δ (ppm) 155.7; 148.0; 137.3; 129.7; 128.8; 128.3; 128.1; 117.3;113.4; 67.3; 51.1; 47.4; 45.0; 42.1; 27.5; 25.4; 18.5.

EXAMPLE 31 Synthesis ofN-[1-(1-phenethylpiperidin-3-yl)ethyl]-N-Phenylpropionamide 23

To a solution of afford 3-(1-phenylaminoethyl)piperidine-1-carboxylicacid tert-butyl ester 22 and N,N-diisopropylethylamine (5 equiv) inCH₂Cl₂ (0.5 M) at 0° C. was added propionyl chloride (3.0 equiv). Thereaction mixture was shaken overnight. The mixture was poured into 10%NaOH, then extracted with EtOAc. The extracts were combined and washedwith aqueous NaHCO₃, dried over sodium sulfate, filtered, andconcentrated. The crude material was purified by column chromatography(silica gel, hexane:EtOAc, 4:1) to giveN-[1-(1-phenethylpiperidin-3-yl)ethyl]-N-Phenylpropionamide 23.

EXAMPLE 32 Synthesis of(3R)-3-[(1R)-1-(Phenyl-propionyl-amino)-ethyl]-piperidine-1-carboxylicacid benzyl ester (18)

A 100 mL round-bottom flask was charged with amine (obtained by S_(N)2displacement of the corresponding triflate) (5.45 g; 16.1 mmol), DCM (20mL) and diisopropylethylamine (5.61 mL: 32.2 mmol). The reaction mixturewas cooled to 0° C. and propionyl chloride (2.80 mL; 32.2 mmol) wasadded. The reaction mixture was stirred at 20° C. for 16 h. The reactionmixture was diluted with EtOAc (1.00 mL). The organic layer was washedwith saturated NaHCO₃ (100 mL), saturated NaCl (100 mL), dried (Na₂SO₄),filtered and concentrated in vacuo. The crude material was purified byflash chromatography (silica gel, hexanes/EtOAc 4:1 to 2:1) to giveproduct (5.72 g, 90% yield). ¹H-NMR (300 MHz) δ (ppm) 7.40 (m; 7H); 7.10(d; 3H); 5.08 (s; 2H); 4.78 (m; 1H); 4.00 (m; 2H); 2.93 (m; 1H); 2.76(t; 1H); 2.05 (m; 1H); 1.98 (q; 2H); 1.80 (m; 2H); 1.50 (m; 4H); 1.02(m; 5H). ¹³C-NMR (300 MHz) δ (ppm) 174.2; 155.4; 139.0; 137.1; 131.0;129.7; 128.7; 128.5; 128.1; 128.0; 67.2; 52.8; 47.5; 44.7; 39.6; 28.8;28.7; 24.9; 17.3; 10.0.

EXAMPLE 33 Synthesis of(3R)-3-[(1S)-1-(Phenyl-propionyl-amino)-ethyl]-piperidine-1-carboxylicacid benzyl ester (20)

A 100 mL round-bottom flask was charged with amine (obtained by S_(N)2displacement of the corresponding mesylate) (1.37 g; 4.05 mmol), THF (25mL), potassium bicarbonate (2.79 g mL: 20.0 mmol) and propionyl chloride(1.76 mL; 20.0 mmol). The reaction mixture was heated to 50° C. andstirred for 16 h. The reaction mixture was cooled to room temperatureand diluted with EtOAc (100 mL). The organic layer was washed withsaturated NaHCO₃ (100 mL), saturated NaCl (100 mL), dried (Na₂SO₄),filtered and concentrated in vacuo. The crude material was purified byflash chromatography (silica gel, hexanes/EtOAc 4:1 to 2:1) to giveproduct (2.28 g, 50% yield). ¹H-NMR (300 MHz) δ (ppm) 7.48 (d; 1H); 7.40(m; 6H); 7.10 (d; 3H); 5.18 (s; 2H); 4.78 (m; 1H); 4.44 (m; 1H); 4.22(m; 1H); 2.78 (m; 2H); 1.98 (m; 2H); 1.80 (m; 4H); 1.40 (m; 2H); 1.02(m; 5H). ¹³C-NMR (300 MHz) δ (ppm) 174.5; 155.0; 138.8; 137.1; 129.5;129.0; 128.8; 128.5; 124.0; 120.1; 67.6; 52.2; 48.6; 44.7; 40.5; 30.8;28.5; 25.5; 17.1; 10.0.

EXAMPLE 34 Synthesis of(3S)-3-[(1R)-1-(Phenyl-propionyl-amino)-ethyl]-piperidine-1-carboxylicacid benzyl ester (35)

A 100 mL round-bottom flask was charged with amine (obtained by S_(N)2displacement of the corresponding mesylate) (250 g; 0.73 mmol), DCM (5mL) and diisopropylethylamine (0.65 mL: 3.65 mmol). The reaction mixturewas cooled to 0° C. and propionyl chloride (0.20 mL; 2.28 mmol) wasadded. The reaction mixture was stirred at 0° C. for 4 h. The reactionmixture was diluted with EtOAc (5 mL). The organic layer was washed withsaturated NaHCO₃ (10 mL), saturated NaCl (10 mL), dried (Na₂SO₄),filtered and concentrated in vacuo. The crude material was purified byflash chromatography (silica gel, hexanes/EtOAc 4:1 to 2:1) to giveproduct (0.165 g, 57% yield). ¹H-NMR (300 MHz) δ (ppm) 7.48 (d; 1H);7.40 (m; 6H); 7.10 (d; 3H); 5.18 (s; 2H); 4.78 (m; 1H); 4.44 (m; 1H);4.22 (m; 1H); 2.78 (m; 2H); 1.98 (m; 2H); 1.80 (m; 4H); 1.40 (m; 2H);1.02 (m; 5H). ¹³C-NMR (300 MHz) δ (ppm) 174.5; 155.0; 138.8; 137.1;129.5; 129.0; 128.8; 128.5; 124.0; 120.1; 67.6; 52.2; 48.6; 44.7; 40.5;30.8; 28.5; 25.5; 17.1; 10.0.

EXAMPLE 35 Synthesis of(3S)-3-[(1S)-1-(Phenyl-propionyl-amino)-ethyl]-piperidine-1-carboxylicacid benzyl ester (36)

A 100 mL round-bottom flask was charged with amine (obtained by S_(N)2displacement of the corresponding mesylate) (0.300 g; 0.88 mmol), DCM (6mL), and diisopropylethylamine (0.78 mL: 4.38 mmol). The reactionmixture was cooled to 0° C. and propionyl chloride (0.24 mL; 2.74 mmol)was added. The reaction mixture was stirred at 0° C. for 4 h. Thereaction mixture was diluted with EtOAc (6 mL). The organic layer waswashed with saturated NaHCO₃ (10 mL), saturated NaCl (10 mL), dried(Na₂SO₄), filtered and concentrated in vacuo. The crude material waspurified by flash chromatography (silica gel, hexanes/EtOAc 4:1 to 2:1)to give product (0.236 g, 68% yield). ¹H-NMR (300 MHz) δ (ppm) 7.40 (m;7H); 7.10 (d; 3H); 5.08 (s; 2H); 4.78 (m; 1H); 4.00 (m; 2H); 2.93 (m;1H); 2.76 (m; 1H); 1.98 (q; 2H); 1.80 (m; 2H); 1.50 (m; 4H); 1.02 (m;5H). ¹³C-NMR (300 MHz) δ (ppm) 174.2; 155.4; 139.0; 137.1; 131.0; 129.7;128.7; 128.5; 128.1; 128.0; 67.2; 53.8; 52.8; 47.5; 44.7; 39.6; 28.8;28.7; 24.9; 17.3; 10.0.

EXAMPLE 36 Synthesis ofN-[1-(1-phenethylpiperidine-3-yl)ethyl]-N-Phenylpropionamide 24

To a solution ofN-[1-(1-phenethylpiperidin-3-yl)ethyl]-N-Phenylpropionamide 23 in CH₂Cl₂(0.45 M) at 0° C. was added TFA. After stirring for 30 min., the solventand excess TFA was removed by evaporation. The residue was dissolved in1.5 mL of CH₃CN, to which K₂CO₃ and (2-bromoethyl)benzene (2 equiv) wereadded. The mixture was stirred at 50° C. overnight. After cooling downto room temperature, 10% NaOH was added. The organic layer wasseparated, and the aqueous layer was extracted with EtOAc. The combinedorganic layers were washed with brine and dried with sodium sulfate,filtered, and concentrated. The crude product was purified by flashsilica gel chromatography (5% MeOH in CH₂Cl₂) to provideN-[1-(1-phenethylpiperidine-3-yl)ethyl]-N-Phenylpropionamide 24.

EXAMPLE 37 Synthesis of(3R)-3-[(1R)-1-(Phenyl-propionyl-amino)-ethyl]-piperidine (37)

A 100 mL Parr shaker-flask was charged with Cbz-protected amine (1.01 g;2.53 mmol) and MeOH (10 mL). The flask was purged with argon and 10%(w/w) Pd/C was added (270 mg; 0.25 mmol). The reaction mixture wasfitted with a hydrogen balloon and hydrogenated at 20° C. for 16 h. Thereaction mixture was filtered through celite and the celite pad washedwith MeOH. The combined organics were concentrated in vacuo to giveproduct (660 mg, 99% yield). ¹H-NMR (300 MHz) δ (ppm) 7.41 (m; 3H); 7.10(d; 2H); 4.75 (m; 1H); 3.25 (dd; 2H); 2.68 (dt; 1H); 2.51 (t; 1H); 2.16(dd; 1H); 1.95 (m; 4H); 1.80 (m; 2H); 1.40 (m; 1H); 1.02 (m; 5H).¹³C-NMR (300 MHz) δ (ppm) 174.4; 139.3; 129.8; 129.5; 128.7; 53.2; 47.6;44.8; 38.5; 28.7; 27.8; 23.2; 17.0; 9.9.

EXAMPLE 38 Synthesis of(3R)-3-[(1S)-1-(Phenyl-propionyl-amino)-ethyl]-piperidine (38)

A 100 mL Parr shaker-flask was charged with Cbz-protected amine (2.28 g;5.70 mmol) and MeOH (10 mL). The flask was purged with argon and 10%(w/w) Pd/C was added (604 mg; 0.57 mmol). The reaction mixture wasfitted with a hydrogen balloon and hydrogenated at 20° C. for 16 h. Thereaction mixture was filtered through celite and the celite pad washedwith MeOH. The combined organics were concentrated in vacuo to giveproduct (1.45 g, 98% yield). ¹H-NMR (300 MHz) δ (ppm) 7.41 (m; 3H); 7.10(d; 2H); 4.78 (m; 1H); 3.50 (d; 1H); 3.23 (d; 1H); 2.79 (t; 2H); 2.00(m; 3H); 1.80 (m; 4H); 1.23 (m; 1H); 1.02 (m; 5H). ¹³C-NMR (300 MHz) δ(ppm) 174.6; 138.7; 130.2; 129.3; 128.76; 52.4; 48.7; 45.2; 38.6; 28.6;27.2; 23.5; 16.9; 9.9.

EXAMPLE 39 Synthesis ofN-[(1R)-1-((3S)-1-Phenethyl-piperidin-3-yl)-ethyl]-N-phenyl-propionamide(2)

A 25 mL round-bottom flask was charged with amine (133 mg; 0.51 mmol),K₂CO₃ (218 mg; 1.5 mmol), MeCN (1 mL), H₂O (1 mL) and phenethyl bromide(84 μL; 0.61 mmol). The reaction mixture was heated to 70° C. andstirred for 3 h. The reaction mixture was cooled to room temperature anddiluted with DCM (50 mL). The organic layer was washed with water (50mL), saturated NaCl (50 mL), dried (Na₂SO₄), filtered and concentratedin vacuo. The crude material was purified chromatography (silica gel,hexanes/EtOAc 4:1 with 2% 2.0 M NH₃ in EtOH) to give pure product (72mg, 40% yield). ¹H-NMR (300 MHz) δ (ppm) 7.42 (m; 5H); 7.21 (t; 2H);6.78 (t; 1H); 6.60 (d; 2H); 5.17 (m, 2H); 4.40 (m; 1H); 4.19 (m; 1H);3.49 (m; 2H); 3.40 (m; 2H); 2.82 (m; 2H); 2.59 (m; 2H); 1.98 (m; 1H);1.78 (m; 1H); 1.57 (m; 2H); 1.22 (m; 2H); 1.18 (d; 3H) 1.05 (m; 1H).¹³C-NMR (300 MHz) δ (ppm) 174.3; 140.7; 139.2; 131.1; 129.8; 129.0;128.6; 126.3; 120.1; 61.2; 58.0; 54.6; 52.8; 40.4; 34.0; 28.8; 28.3;25.7; 17.4; 10.3.

EXAMPLE 40 Chiral Chromatographic Purification of Stereoisomers ofN-[1-(1-phenethyl-piperidin-3-yl)-ethyl]-N-phenyl-propionamide (24)

The chromatographic conditions to separate the four (1, 2, 3, and 4)possible stereoisomers of compound 24 are described below. Thechromatographic conditions generated the chromatographic separationdepicted in FIG. 40.

Column: Chiralcel OD, 10 um, 4.6 × 250 mm Mobile Phase:Hexane/Ethanol/Methanol/Diethylamine (98:0.5:1.5:0.1) Flow Rate: 0.7mL/min Detection: UV 220 nm Temperature: Ambient

Identification of each peak was made by comparison authentic samples ofeach isomer ofN-[1-(1-phenethyl-piperidin-3-yl)-ethyl]-N-phenyl-propionamide (24).This chiral HPLC method was used to analyze 2 obtained from Example 39.See FIG. 41. Using peak area normalization to quantitate the amounts ofindividual isomers in this sample, the following results were obtainedfor the sample.

% de % ee %2 %3 %1 %4 major major Sample (R,S) (S,R) (R,R) (S,S) isomerisomer Example 39 95.46 0.14 1.67 2.73 91.2% 99.7%

EXAMPLE 41 Achiral (Reverse-phase) HPLC Analysis of 15 (See FIG. 16)

FIG. 16 depicts a series of HPLC analyses (at both 254 and 220 nm) ofcompound 15 (8.42 mm) alone in the first two analyses, compound 15co-injected with a mixture of compounds 15 and 16 in the 3^(rd) and4^(th) analyses, and of a mixture of compounds 15 and 16 in the 5^(th)and 6^(th) analyses. The peak at 8.78 mm. is an impurity.

EXAMPLE 42 Achiral (Reverse-phase) HPLC Analysis of 16 (See FIG. 17)

FIG. 17 depicts a series of HPLC analyses (at both 254 and 220 nm) ofcompound 16 (8.16 mm) alone in the first two analyses, compound 16co-injected with a mixture of compounds 15 and 16 in the 3^(rd) and4^(th) analyses, and of a mixture of compounds 15 and 16 in the 5^(th)and 6^(th) analyses.

EXAMPLE 43 Achiral (Reverse-phase) HPLC Analyses of 15 and 16 (See FIG.18)

FIG. 18 depicts a series of HPLC analyses (at both 254 and 220 nm) ofcompound 15 (8.42 mm) alone in the first two analyses, compound 15co-injected with compound 16 in the 3^(rd) and 4^(th) analyses, andcompound 16 in the 5^(th) and 6^(th) analyses.

EXAMPLE 44 Achiral (Reverse-phase) HPLC Analyses of 15 Under a Varietyof Reaction Conditions (See FIG. 19)

FIG. 19 depicts a series of HPLC analyses (at 254 nm) of compound 15(8.8 min) obtained from a variety of experiments run simultaneously andwith differing conditions for each reaction. The first two plots arewith 20 mol % of catalyst 13. The first reaction used solvents distilledfrom sodium/benzophenone under argon, and the second used solventspurchased anhydrous from Aldrich and dried with activated 4 Å molecularsieves. The 3^(rd) and 4^(th) plots are with 10 mol % of catalyst 13.The 3^(rd) reaction used solvent distilled from sodium/benzophenoneunder argon, and the 4^(th) experiment used anhydrous solvents pre-driedwith activated 4 Å molecular sieves. The 5^(th) and 6^(th) plots are forexperiments which used 5 mol % of catalyst 13. The 5^(th) reaction usedsolvent distilled from sodium/benzophenone under argon, and the 6^(th)experiment used anhydrous solvents pre-dried with activated 4 Åmolecular sieves. The 7^(th) plot is a co-injection of compound 15obtained from the first reaction (plot 1) with 16 (8.3 min).

EXAMPLE 45 Opiate Receptor Binding of Certain Enantiomerically Pure3-Substituted Piperidines (IC₅₀s)

The opioid (μ, κ, δ) receptor-binding capabilities of compounds preparedusing the methods of the present invention were determined according tothe procedures outlined by Wang et al. (FEBS Letters 1994, 338, 217),Maguire et al. (Eur. J. Pharmacol. 1992, 213, 219), and Simonin et al.(Mol. Pharmacol. 1994, 46, 1015). Certain results from these assays aretabulated below.

μ κ δ Compound (μM) (μM) (μM) 1 <1 <1 <10 2 <1 <5 >10 3 <1 <5 >10 4 <1<1 >10

Incorporation by Reference

All of the patents and publications cited herein are hereby incorporatedby reference.

Equivalents

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

1. A compound of formula I:

wherein n is 1; R is aralkyl; R′ is alkyl; Z is NHR″; and R″ isunsubstituted aryl.
 2. The compound of claim 1, wherein R is —CH₂CH₂Ph.3. The compound of claim 1, wherein R′ is methyl.
 4. The compound ofclaim 1, wherein R″ is phenyl.
 5. The compound of claim 1, wherein R′ isMe; and R″ is phenyl.
 6. The compound of claim 1, wherein R is—CH₂CH₂Ph; and R′ is methyl.
 7. The compound of claim 1, wherein R is—CH₂CH₂Ph; R′ is methyl; and R″ is phenyl.
 8. A compound of formula II:

wherein n is 1; R is aralkyl; R′ is alkyl; Z is NHR″; and R″ isunsubstituted aryl.
 9. The compound of claim 8, wherein R is —CH₂CH₂Ph.10. The compound of claim 8, wherein R′ is methyl.
 11. The compound ofclaim 8, wherein R″ is phenyl.
 12. The compound of claim 8, wherein R′is Me; and R″ is phenyl.
 13. The compound of claim 8, wherein R is—CH₂CH₂Ph; and R′ is methyl.
 14. The compound of claim 8, wherein R is—CH₂CH₂Ph; R′ is methyl; and R″ is phenyl.
 15. A compound of formulaIII:

wherein n is 1; R is aralkyl; R′ is alkyl; Z is NHR″; and R″ isunsubstituted aryl.
 16. The compound of claim 15, wherein R is—CH₂CH₂Ph.
 17. The compound of claim 15, wherein R′ is methyl.
 18. Thecompound of claim 15, wherein Z is R″ is phenyl.
 19. The compound ofclaim 15, wherein R′ is Me; and R″ is phenyl.
 20. The compound of claim15, wherein R is —CH₂CH₂Ph; and R′ is methyl.
 21. The compound of claim15, wherein R is —CH₂CH₂Ph; R′ is methyl; and R″ is phenyl.
 22. Acompound of formula IV:

wherein n is 1; R is aralkyl; R′ is alkyl; Z is NHR″; and R″ isunsubstituted aryl.
 23. The compound of claim 22, wherein R is—CH₂CH₂Ph.
 24. The compound of claim 22, wherein R′ is methyl.
 25. Thecompound of claim 22, wherein R″ is phenyl.
 26. The compound of claim22, wherein R′ is Me; and R″ is phenyl.
 27. The compound of claim 22,wherein R is —CH₂CH₂Ph; and R′ is methyl.
 28. The compound of claim 22,wherein R is —CH₂CH₂Ph; R′ is methyl; and R″ is phenyl.